02 Introduction to Minitab

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Lean Six Sigma Operational - Delegate Workbook

SSG06101ENUK Minitab1/Issue 1.2/ July 2008 1 The British Standards Institution 2008

Introduction to Minitab

2

SSG06101ENUK Delegate Slides /Issue 2.2/ July 2008

What is Minitab?

Minitab is a powerful statistical software package

that removes much of the pain associated with

analysing data and using statistical tools

This module provides an introduction andoverview of its use


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Section 1 - Introducing theSoftware

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Contents of this Section

Introduction to the Software

Navigating using the Project Manager

Data in Minitab

Data types

Changing Data types

Minitab Overview

Opening Worksheets

Worksheet Folder

Worksheet Description

Column Description

Data Structure and Manipulation

Subset/Split Worksheets

Information Folder


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5


Opening MinitabMenu Bar

Tool Bar

The Session Window

The Worksheet/Data Window

Project Manager Window

(minimised)

By default Minitab opens with the above

Contains the data,similar to a spreadsheet

Acts like a windows explorer ,

A chronological history of the analysis

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Minitab Worksheet

Worksheet looks like Excel spreadsheet, but be aware that: you cannot write formulae based on cells most operations work onwholecolumns of data any text in a cell will format the column as a Text Column, labelled Cn-T, which prevents any mathematical analysis on that column grey first row is for column names only, not for data two columns cannot have the same name in any one worksheet

Worksheet looks like Excel spreadsheet, but be aware that: You cannot write formulae based on cells, unless you use the calculator Most operations work onwholecolumns of data Any text in a cell will format the column as a Text Column, labelled Cn-T

which prevents any mathematical analysis on that column Grey first row is for column names only, not for data Two columns cannot have the same name in any one worksheet


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7


Minitab FilesThere are two basic types of Minitab file

1. Minitab Projects; filename.MPJ

Worksheets Graphs

Session Window Output Session Command History

2. Minitab Worksheets; filename.MTW

Columns Constants

Matrices Column DescriptionsWorksheet Descriptions

Save your work as a Minitab Project File in order to save all your data,graphs, preferences together.

If you save your work as a Worksheet file, you only save the data.

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Minitab Windows

Project Manager

Manage worksheets, output

Graphs, and related

documents

(Shortcut keys - Ctrl + l )

Session Window

View Statistical Output and

enter Session Commands(Shortcut keys - Ctrl + M )

Data Window

View and Edit Worksheets

(Shortcut keys - Ctrl + D )

Project

documents

(Shortcut keys - Ctrl + l )

Session

View

enter(Shortcut keys - Ctrl + M )

Data

View and

(Shortcut keys - Ctrl + D )


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9


Navigating with the Project Manager

Folder View

Shows all elementsof a project

Left pane shows thefolders

Right pane showsthe content of theactive folder

Toolbar View

Detached by clicking on

and dragging

Folder

Shows all elementsof a project

Left pane shows thefolders

Right pane showsthe content of theactive folder

Toolbar

Detached by clicking on

and dragging

10


Minitab the Project Manager Toolbar

Open the Session Folder View Statistical Output

Open the Worksheet Folder Accesses all Worksheets

Open the Graphs Folder Access and Manage Graphs

Open the Show Info Folder Column Descriptions Constants

Open the History Folder Access Command Language

Open the Report Pad Create and Store Reports

Show the Related Documents Folder links to files

Open the

Open the

Open the

Open the

Open the


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11


Data Types in Minitab

In the next slide you will initially see three data types in a

Minitab worksheet:

Numeric Data for example, man hours spent on a particular

task

Text Data for example, the name of the department involved

Date/ Time Data for example, when a particular data item was

measured or collected

In this example, the company concerned is starting to take aclose look at where cost occurs in a particular process

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Data Types in Minitab

Minitab operatesusing columns ofdata.

The arrow indicates

the direction that thedata is entered in.Click on the arrow tochange its direction.

The names of thecolumns are enteredabove the column(not in row 1)

MInitab (automatically) recognisesseveral different types of data: Numeric

Date/Time (D)

using columns of

The arrow indicates

the direction that thedata is entered in.Click on the arrow tochange its direction.

The names of thecolumns are enteredabove the column(not in row 1)

several different types of data:

Numeric

Text (T)


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Entering Data in MinitabData can be entered into

Minitab in a variety ofways:

1) Manually

2) Cutting and pasting fromother applications likeExcel

3) Opening a worksheet

from another softwareapplication directly intoMinitab

Because Minitab columns

work top-down, missingdata is represented by anasterisk.

Data can be entered into

ways:

1) Manually



from another softwareapplication directly into work top-down, missingdata is represented by an

asterisk.


ways:

1) Manually




asterisk.


ways:

1) Manually




asterisk.

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Changing Data Types in Minitab (1)

Sometimes Minitab makesmistakes in recognising thetype of data in a column.

Eg : When you cut and paste

data, just one piece of textwill cause the whole columnto be labelled as text, asshown.

Unfortunately, deleting the text wont change the columntype back automatically. This needs to be done manually

see next page.

mistakes in recognising thetype of data in a column.

: When you cut and paste

data, just one piece of textwill cause the whole columnto be labelled as text, asshown.

Unfortunately, deleting the text wont change the columntype back automatically. This needs to be done manually

see next page.


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15


Changing Data Types in Minitab (2)

NB: You can delete the text data before using this function, butdont need to.

MINITAB: Data > Change Data Type > Text to Numeric

This function is set to change all the data in column C5 (days) tonumeric data, and store it back in C5.

NB: You can delete the text data before using this function, but youdont need to.

Minitab: Data > Change Data Type > Text to Numeric

This function is set to change all the data in column C5 (

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Importing Data from ExcelIt is possible to import Excel worksheets directly into Minitab,but check the format

of the data first. Remember that Minitab only allows one row for the column

headings, and the Excel worksheet needs to reflect this.

File > Open > MINITAB Worksheet

Under Files Of Typechoose

Excel (*.xls), as below.

Find and Open the data worksheet:

Car Fleet Mileage Data-July.xls

It is possible to import Excel worksheets directly into

of the data first. Remember that

headings, and the Excel worksheet needs to reflect this.

File > Open Worksheet

Under

Excel (*.xls), as below.

-July.xls


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The following example introduces the basic functions ofMinitab and demonstrates the key navigation tools.

The example includes three worksheets:1 - Stacked data all the data in a stacked format2 Shift the data unstacked by shift3 Region the data unstacked by region

Normally, Minitab files are saved as Minitab projects,which have the file extension MPJ.

Find and Open the file Unavailability.mpjby double clicking on it from within Windows Explorer.

Minitab Overview

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Minitab Show Worksheets Folder

Click on the

Project manager

Toolbar

The live worksheet isshown by a greenfolder and asterisksafter its header

To make worksheets

active double-clickthe folder icon next

to the worksheet

name.

Click on the

The live worksheet isshown by afolder and asterisksafter its header

To make worksheets

active double-clickthe folder icon next

to the worksheet

name.

Call Centre study:Note that

unavailability is theunavailable time as apercentage of the totaltime across both callcentre location andshift..


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Worksheet Descriptions in MinitabTo add or edit an existing worksheet description click anywhere

in the relevant worksheet, then select:

Editor > Worksheet > description

Red triangle:

Indicates that there is a

worksheet description

present.

Hold the cursor over thetriangle to view, or double

click to edit.

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Column Descriptions in MinitabTo add or edit an existing column description click therelevant column, then select:

Editor > Column > Description

Red Triangle:

denotes anavailable Columndescription.

Hover the cursorover the triangle toview or double clickto edit.

To add or edit an existing column description click therelevant column, then select:

Editor > Column > Description

Red

denotes anavailabledescription.

Hover the cursorover the triangle toview or double clickto edit.


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Data Structure And Manipulation (1)

Jan Feb Mar Apr

Location 1 289 295 300 301

Location 2 70 73 75 76

Location 3 168 174 180 189

Minitab operates using columns of data.

So, wheretraditionally we mightstructure data likethis:

In Minitab, the data

should be structuredin columns like these:

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Data Structure and Manipulation (2)

Comparing old versus new (&improved?) processes

Open a new worksheet of rawdata

The next step is to include

categories against the data.

1.Sample Number

2.Time of Sample

File > Open Worksheet > OldversusNew.mpj

Open a new worksheet of rawdata

The next step is to include

categories against the data.

1.

2.Time of

File > Open Project > OldversusNew.mpj


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Data Structure and Manipulation (3)The sample number andthe time that the data was

recorded could be added.

Minitabs ability to create

patterned data could be

useful here (see nextpage).

Name columns C3 and C4

as shown.

NB: Note that Minitabmust have unique column

names.

The sample number andthe time that the data was

recorded could be added.

patterned data could be

useful here (see nextpage).

Name columns C3 and C4

as shown.

NB: Note thatmust have unique column

names.

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Data Structure and Manipulation (4)Exercise:Use Minitabs Patterned data function as shown tocreate a set of sample numbers in Column 3 (C3).

Calc > Make Patterned Data > Simple Set of Numbers

Where do want thedata to be stored?

What number do youwant the column tostart at?

What number do youwant the column tofinish at?

Exercise:Usecreate a set of sample numbers in

Calc > Make Patterned Data > Simple Set of Numbers


What number do youwant the column tostart at?

What number do youwant the column tofinish at?


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Data Structure and Manipulation (5)Exercise:Use Minitab s Patterned data function as shown tocreate a set of sample numbers in Column 4 (C4).

Calc > Make Patterned Data > Simple Set of Date/Time Numbers


When does thesequence start?

When does thesequence finish?

What increment

between values?Unit of increment?

Exercise:Usecreate a set of sample numbers in

Calc > Make Patterned Data > Simple Set of Date/Time Numbers


When does thesequence start?

When does thesequence finish?

What increment

between values?Unit of increment?

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Your data should now look like this:

Note that the heading of Column 4 has a

D Suffix, because it is a date/time

format.

Before analysing the data, you need to

check all the different types of data havetheir own column.

Columns 1 and 2 contain the same type

of data, so would be better placed in the

same column. Minitab can stack data

like this into one column;

next page.

Your data should now look like this:

Note that the heading of

D

format.

Before analysing the data, you need to

check all the different types of data havetheir own column.

Columns 1 and 2 contain the same type

of data, so would be better placed in the

same column.

like this into one column;see

next page.


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Data Structure and Manipulation (7)What are we trying to do by stacking the data?

Answer: we would like to have one column containing the measured data(from C1 and C2).

Data > Stack > ColumnsPlace all the columnsto be stacked here.

Decide where youwant the data to go.

Name the newcolumns

Tick to use originalcolumn names whenstacked

What are we trying to do by stacking the data?

d data(from C1 and C2).

Data > stack > columnsPlace all the columnsto be stacked here

Decide where youwant the data to go

Name the newcolumns

Tick to use originalcolumn names whenstacked

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The resulting data set looks likethis:

The stacked data has beenplaced in C5, with a subscriptin C6.

A subscript defines acharacteristic of the data - in thiscase whether it was from the oldor new process.

Exercise: Copy and paste the

Time Data manually into C7, asshown here, and save the project


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Subset/Splitting out data

Subset WorksheetFunction:Use to copy specified rows from the active worksheet to anew worksheet. You can specify the subset based on rownumbers, brushed points on a graph, or a condition suchas unmarried males under 50 years old.

Split WorksheetFunctionSplits, or unstacks, the active worksheet into two or morenew worksheets based on one or more by" variables.

Subset Worksheetand Split Worksheetalways copy datato new worksheets. You can use Copy Columnsto replacedata in the current worksheet with a subset.

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Subset Worksheet (1)

Using the Unavailability.mpjfile again:

We want to separate out the dataat point 25 where it changes fromCentral to Western

A key point here is that we shouldalways retain the original raw datafile intact.

Therefore, we could use thesubset worksheetfunction.

Using the Unavailability.mpjfile again:

We want to separate out the dataat point 25 where it changes from

A key point here is that we shouldalways retain the original raw datafile intact.


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In name enter Central

Click specify which rows toinclude

Click row numbers and enterthe row numbers in the box.

You can enter either everynumber 1 2 3 4 5 etc or enterthe range 1:24

NB: The colon is essential

The result is shown on the next page

Data > Subset Worksheet

Central

Click include

Click row numbers and enterthe row numbers in the box.

You can enter either everynumber 1 2 3 4 5 etc or enterthe range 1:24

NB: The colon is essential

The result is shown on the next page

Data > Subset Worksheet

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A separate worksheet for the Central data has been created and theoriginal raw data file for all centres has been retained.

This can now be repeated for Western and Eastern data


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Subset Worksheet (4)If we click on the

Show Worksheets icon

Project Manager shows

the original worksheet andthe newly created ones forCentral, Western and

Eastern.

The Green Folder shows

which folder is currentlyactive.

If we want to separate the worksheet by shift, we would thenuse Split Worksheet

If we click on the

icon

the original worksheet andthe newly created ones forCentral, Western and

Eastern.


If we want to separate the worksheet by shift, we would then

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Split Worksheet (1)The Split Worksheet function will create two or more worksheets from anoriginal data file

Example: Split Stacked Data into three separate worksheets, one for eachshift

Data > Split Worksheet

Enter Shift under ByVariables

Click OK


Enter under

Click OK


Enter under

Click OK


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Split Worksheet (2)Minitab will then create three new worksheets one for eachShift

NB. The active worksheet is identified by the 3 AsterisksNB. The active worksheet is identified by the 3

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Split Worksheet (3)

If we click on the

Show worksheets icon, theProject Manager shows theoriginal worksheet and thenewly created ones forShift 1, Shift 2 and Shift 3.

The green folder showswhich folder is currentlyactive.

If we click on the

original worksheet and thenewly created ones for



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The Info FolderMinitabs Project Manager can be used to provide a summary

of the worksheet. Click here for information .

The infowindow can be useful for identifying missing data etc,particularly on large worksheets.

of the worksheet. Click here for information .

The infowindow can be useful for identifying missing data etc,particularly on large worksheets.

Section 2 - Analysing theData


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Contents of this section

Minitabs Functions Statistical & Graphical

Accessing the Stat Guide

Minitab Graphs Updating

Displaying Basic Statistics

Graphical summary

Scatterplot and Brushing

Bar Chart Changing colours of bars Adding reference lines

Time Series plot

Histogram

Boxplot

Dotplot

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Analysing the Data using Graphs

Graphing (or plotting) is one of the most powerful tools of theSix Sigma process. By reading graphs they will often tell youthe story of the process.

The statistics can then be used to provide mathematical

confidence in the conclusions you draw from the graphs.

In the following pages we look at the following graphs inMinitab:

Basic Statistics Scatterplots

Bar Chart HistogramsTime Series Plots Box Plot

Graphing is alwaysthe first step of analysing data


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Minitabs Statistical FunctionsMinitab Stat menucontains all of thestatistical functions thatyou will need within SixSigma.

Basic Statisticscontains the most

frequently usedcommands.

s contains all of thestatistical functions thatyou will need within SixSigma.

Basic contains the most


contains all of thestatistical functions thatyou will need within SixSigma.

Basic contains the most


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Minitabs Graphical Functions (1)

Minitabs Graph menu contains all of thegraphical functions that you will need withinSix Sigma.

For correlations

For plotting distributions

For comparing groups of data

For analysing categories

For studying trends over time

For 3D graphs

graphical functions that you will need withinSix Sigma.


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Minitabs Graphical Functions (2)Almost all of Minitab graphs can be accessed through severaldifferent menu locations. For example

Stat > Basic Stats > Display Descriptive Stats

An Individual Value Plotof column C1(Old data) can be created through thegraph options of the DisplayDescriptive Statisticsfunction, asshown on the left.

s

Stat > Basic Stats > Display Descriptive Stats

An

function, asshown on the left.

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Minitabs Graphical Functions (3)

Graph > Individual Value Plot

An Individual Value Plotof column C1 (Old data) can also be createdthrough the Graph menu, as shown below

Exercise:Create Individual Value Plots for the Old data (C1) using thetwo methods shown on the last two slides.

Graph > Individual Value Plot

An

Exercise: data (C1) using thetwo methods shown on the last two slides.


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Minitabs Graphical Functions (4)The Individual Value Plotsbelow show the same data, but look differentbecause they were created in different ways in Minitab.

Exercise: Take a closer look at the graphics in the top left hand cornethe graph windows youve created.

Now go back to the data in the worksheet and change one of the vthe old Column. What happens to the graphics?

The below show the same data, but look different

Exercise: Take a closer look at the graphics in the top left hand corner ofthe graph windows youve created.

Now go back to the data in the worksheet and change one of the values inthe

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Accessing the Stat Guide

Minitabs StatGuidehelps to interpret the results of the analyses.

Contextual help is available form all input dialogue boxes


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Minitabs Graphs Updating (1)graph in Minitab, and subsequently change the source data, the graph

does not necessarilyupdate itself.

Some graphs do not have the capability to be updated. In this c

A green cross indicates the graph is up to date

And a white cross indicates the graph is not

up to date, and cannot be updated


Some graphs do not have the capability to be updated. In this c


Unlike common spreadsheet packages such as Excel, when you create a


Some graphs do not have the capability to be updated. In this case


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Minitabs Graphs Updating (2)Some graphsdohave the capability to be updated. In this case

A green cross on white indicates the graph is up to date

and a yellow circle indicates the graph is notup to date, but can be updated

Graphs can be updated by right-clicking the graph and selecting:Update Graph Automatically

or Update Graph Now


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Minitabs Basic Statistics (1)Minitab has a wide variety of ways of displaying data. The following is auseful tool.

Stat > Basic Statistics > Descriptive Statistics

Double click on old and

New to place them in the

variables box

Click Statistics

useful tool.


Double click on


Click


Double click on


Click

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Minitabs Basic Statistics (2)

Trimmed Mean: The top and bottom 5% of data is ignored in calculatingthis version of the mean (average).

Minitab gives the option to select a number of different statistFor example, check Trimmed Mean

Click OK

this version of the mean (average).

Minitab gives the option to select a number of different statisticsFor example, check

Click OK


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Minitabs Basic Statistics (3)The output from this function appears in the Session Window.

Trimmedmean

Trimmed Mean When the Trimmed Mean is very close to the StandardMean it shows the absence of significant outliers.

First andThird quartile

Trimmedmean

First andThird quartile

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Minitabs Basic Statistics (4)This information can also be shown graphically. Select:

Stat > Basic Statistics > Graphical Summary

Double click on

Old and New

Click OK

This information can also be shown graphically. Select:

Stat > Basic Statistics > Graphical Summary

Double click on

Click OK


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Minitabs Basic Statistics (5)

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Scatter Plots (1)What do we want to know?How does the output from the Old process compare to the output from theNew process?

The first step is to select thetype of Scatter Plot yourequire.

In this case, select Simple

Click Simple

Graph > Scatter Plot > Simple

What do we want to know?

Graph > Scatter Plot > Simple


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Scatter Plots (2)

Firstly, double leftclick on Oldtoplace it in the Y box

Then double left clickon Newto place it inthe X box

Click OK

The Scatter Plot will graph point 1 of the Olddata against point 1 of theNewdata, then point 2 of the Oldagainst point 2 of the Newand so on.

Firstly, double leftclick on toplace it in the Y box

Then double left clickon to place it in

Click OK

data, then point 2 of the against point 2 of the and so on.

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Scatter Plots (3)

Analysis:

The alignment isnt perfect, but itlooks like the old and new

processes produce about thesame outputexcept for onesmall detail

The scales are not the same!

In order to see a true

representation then the X axis

and the Y axis must be scaledthe same.

If the two processes are producing the same outputs, we would ex

Scatter Plot to show a 45 degree line through the origin.

The output should look like this:Analysis:

The alignment isnt perfect, but it

processes produce about thesame outputsmall detail

The scales are not the same!

In order to see a true

representation then the X axis

and the Y axis must be scaledthe same.

If the two processes are producing the same outputs, we would expect a

The output should look like this:


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Scatter Plots (4)To adjust the ScatterPlot with axes of the thesame scale, then followthis process:

Click on Y axis

Select: Editor

thesame scale, then followthis process:

Select: Edit Y Scale

Check same scale range for

Y and X

Click OK

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Scatter Plots (5)

Question: Are the two processes producing the same results?If not, how are they different?

Question: Are the two processes producing the same results?If not, how are they different?


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Minitab Graphs - BrushingSome Minitab graphs can also be interrogated using the Brush function,found under the menu: Editor > Brush

Exercise: Practice using the Brush function on the Scatter Plots that youvecreated. Note that the Brush function can only be used on graphs that areup to date.

The Brush function allows you tobrush over specific points on agraph, and a smaller window thenappears to give you the rownumbers of those data points.

Exercise

up to date.

brush over specific points on agraph, and a smaller window thenappears to give you the rownumbers of those data points.

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Bar Charts (1)What do we want to know?How do we graphically summarise frequency data where there are scategorical variables?

Open the file:

Under bars represent chooseA function of a variable

Under one Y choose cluster

Click OK

Graph > Bar Chart

Unavailability.MPJ

What do we want to know?How do we graphically summarise frequency data where there are severalcategorical variables?

Open the file:

A function of a variable

Click OK

Graph > Bar Chart

Unavailability.MPJ


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In the Graph Variablesbox enter Unavailability

Under categoricalvariables enter, Call

Centrethen Shift

Click OK

Bar Charts (2)

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Bar Charts (3)Interpreting the results...

Why does the level ofUnavailability over thethree shifts decline inCentral and increase in

Western?

Why is the level ofUnavailability on Shift 2 somuch higher in Easternthan the other tworegions?

Minitab can cluster the data by regions within the shifts

In Minitab press the shortcut keys. CTRL-E to bring back your last dialogue

box. Now enter the Categorical variables in the order Shift, then Call Centre.

Does this tell us anything different?

Why does the level of

three shifts decline inCentral and

Western?

Why is the level of

much higher in Easternthan the other tworegions?

Shift, then

Does this tell us anything different?


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Bar Charts (4)Changing the colours of the bars

Editor > Edit bars

Click once any bar on the chart and Minitab will highlight all the bars.

Once the bars are highlighted, select:

In the dialogue box clickGroups

Enter Shift in Categoricalvariables

Click OK

Changing the colours of the bars

Editor > Edit Bars

Once the bars are highlighted, select:

In the dialogue box click

variables

Click OK

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Bar Charts (5)Changing the colours of the barsChanging the colours of the bars


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Bar Charts - Adding Reference Lines

We can add these reference lines to the chart. Firstly right click the greyarea around the graph and select :

Add > Reference Lines

Complete the dialogue box withthe 3%, 4% and 5% targets

(remember to leave a spacebetween each number)

Click OK

Management may want to know where each region performed against

targets of 3%, 4% and 5%.

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Target

Lines

Bar Charts - Adding Reference Lines


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Time Series Plots (1)

Check


Because our data is time ordered we should look to see if there

Graph > Time Series Plot > Simple

Click OK


Because our data is time ordered we should look to see if there are anypatterns over time. Open the file OldversusNew.mpj

Graph > Time Series Plot > Simple

Select Old and New,thenclick on Multiple Graphs

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Time Series Plots (2)The Time Series Plotappears to show that thenew process is givingslightly higher figures

(overall) than the old

process.

This confirms what wasseen in the Scatter Plot.

Remember the Time

Series Plot gives asequential view.Index

20161284

12.975

12.950

12.925

12.900

12.875

12.850

20161284

Old New

TimeSeriesPlotof Old, New

We can now superimpose the New process onto the Old process toconfirm this difference between New and Old.

appears to show that the

slightly higher figures

process.

This confirms what was

sequential view.Index20161284

12.975

12.950

12.925

12.900

12.875

12.850

20161284

Old New

TimeSeriesPlotof Old, New


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Time Series Plots (3)To superimpose the two Time Series Plots directly on top of each other

Double click onOld

Double click onNew

Click OK

Graph > Time Series Plot > Multiple

Click OK

Graph > Time Series Plot > Multiple

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This version showsclearly that not only

does the newprocess take longerthan the Old, but

also both sets ofdata are followingvirtually the samepattern over thetwenty readings.Index

Data

2018161412108642

12.975

12.950

12.925

12.900

12.875

12.850

Variable

Old

New

Time Series Plot of Old, New

Time Series Plots (4)


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Histograms (1)Continuing with graphical analysisThe two processes in the previous graphs appear to be different, and soit may be worth investigating the distributions within each process tounderstand their differences.

Double click on Old toplace it in Graph 1

Double click on Newto place it in Graph 2

Click Multiple Graphs

Graph > Histogram > Simple

Continuing with graphical analysisThe two processes in the previous graphs appear to be different, and soit may be worth investigating the distributions within each process tounderstand their differences.

Double click on

Double click on

Graph > Histogram > Simple

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Histograms (2)The Multiple Graphscommand enables you to plot 2 graphs side by side,using the same scale for comparison

Click in separate panelsof the same graph

Tick Same Y and Same X

The command enables you to plot 2 graphs side by side,using the same scale for comparison.

Click of the same graph

Click OK


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Histograms (3)

Frequency

12.9612.9412.9212.9012.8812.86

7

6

5

4

3

2

1

0

12.9612.9412.9212.9012.8812.86

Old New

Histogram of Old, NewAlthough the processes look

very similar the Newprocess

seems to be producingslightly higher figures.

It might be useful to have the

Newgraph sitting above the

Oldgraph.

Right click the graph

Select Panel, then Arrangement

Choose Custom Enter 2 in Rows and 1 in

columns

Click OK

Although the processes look

very similar the process

seems to be producingslightly higher figures.

It might be useful to have the

graph sitting above the

columns

Click OK

74


Histograms (4)

Frequency

8

6

4

2

0

1 2 . 9 61 2 . 9 41 2 . 9 21 2 . 9 01 2 . 8 81 2 . 8 6

8

6

4

2

0

Ol d

Ne w

Histogr am of O ld , Ne w

The observation that the New process appears to be producing slightly

higher figures than the Old process is now much easier to see.


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Histograms (5)We can also get Minitab to fit a distribution line on to the Histogram

Frequency

12.9612.9412.9212.9012.8812.86

7

6

5

4

3

2

1

0

12.9612.9412.9212.9012.8812.86

Old Ne w O ld

12.92

S t D e v 0 . 02 1 05

N 20

M ea n 12 .90

S t D e v 0 . 01 9 16

N 20

New

Mean

Histogram of Old, NewN orma l

Graph > Histogram > With Fit

Frequency

12.9612.9412.9212.9012.8812.86

7

6

5

4

3

2

1

0

12.9612.9412.9212.9012.8812.86

Old Ne w O ld

12.92

S t D e v 0 . 02 1 05

N 20

M ea n 12 .90

S t D e v 0 . 01 9 16

N 20

New

Mean

Histogram of Old, NewN orma l

Graph > Histogram > With Fit

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Boxplots (1)

A Boxplot is a tool for observing differences in position and/orspread between data groups

They are often used before more advanced statistical HypothesisTests such as t-Tests, f-Tests, ANOVA etc

They are particularly useful during the Analyse Phase, to dividedata out by rational sub-groups. This can help identify potentially

critical Xs and sources of non-normality

If data has been well collected then it can be stratified into rationalsub-groups, by logical factors such as:

Shift Number

Equipment Type

Order Number

Day of the Week

Operator


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Boxplots (2)

Double click OldandNewto place them in theGraph Variables box.

In this first example weare comparing the outputof the two processes, Oldand New.

Click OK

Graph > Boxplot > Multiple Ys - Simple

Double click andto place them in the

In this first example weare comparing the output

Click OK

Graph > Boxplot > Multiple Ys - Simple

78


Data

NewOld

12.975

12.950

12.925

12.900

12.875

12.850

Boxplot of Old, New

Data

NewOld

12.975

12.950

12.925

12.900

12.875

12.850

Boxplot of Old, New

Structure of a Boxplot:The vertical lines above and below the box are Whiskers and represent thetails of the distribution. The Box represents the middle 50% of the data, andthe horizontal line in the box is the Median or the mid point of the data. Aquartile represents one quarter of the data.So in this example what does the Boxplot tells us about the processes?

Structure of a :

quartile represents one quarter of the data.

3rd QuartileData rangeindicated byWhiskers(excludingoutliers)

3rd Quartile

Median

1st Quartile

Data rangeindicated by

Boxplots (3)


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Boxplots (4)

Place the data to be

plotted under Graph

Variable

In this case we want to

show different Boxplots

for the different time

periods that data was

gathered, so placeTime

in Categorical Variables.

Click OK

Graph > Boxplot > One Y With Groups

Place the data to be

plotted under


show different

for the different time

periods that data was

gathered, so place

in .

Click OK

Graph > Boxplot > One Y With Groups

80


Boxplots (5)

Time

Old

09:00pm06:00pm03:00pm12:00 pm09:00am

12.950

12.925

12.900

12.875

12.850

Time

New

09:00pm06:00pm03:00pm12:00pm09:00 am

12.96

12.94

12.92

12.90

12.88

Boxplot of Oldvs Time Boxplot of Newvs Time

From these boxplots , immediate points for investigation stand out:

1. Why a wider spread of data on both processes at 9:00 am?

2. Why are the results at 6:00pm higher in both processes?

Editor > Layout Tool

Time

Old

09:00pm06:00pm03:00pm12:00 pm09:00am

12.950

12.925

12.900

12.875

12.850

Time

New

09:00pm06:00pm03:00pm12:00pm09:00 am

12.96

12.94

12.92

12.90

12.88

Boxplot of Oldvs Time Boxplot of Newvs Time

From these Boxplots, immediate points for investigation stand out:

1. Why a wider spread of data on both processes at 9:00 am?

2. Why are the results at 6:00pm higher in both processes?

Editor > Layout tool


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Boxplots (6)We can, if we wish, put both of these charts on to one chart.

Place the data columns to

be plotted under Graph

Variables


show different Boxplots for

the different times

data was gathered, so

enter Timeunder

Categorical Variables

Click OK

Graph > Boxplot > Multiple Ys With Groups

We can, if we wish, put both of these charts on to one chart.

Place the data columns to

be plotted under


show different for

the different times

data was gathered, so

enter under

Click OK

Graph > Boxplot > Multiple Ys With Groups

82


Data

Time

New

Old

09:00pm

06:00pm

03:00pm

12:00pm

09:00am

09:00pm

06:00pm

03:00pm

12:00pm

09:00am

12.975

12.950

12.925

12.900

12.875

12.850

Boxplot of Old, New vs Time

Boxplots (7)


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Dotplots (1)Another useful graphical tool is the Dotplot.

Enter the columns to begraphed in Graph Variables

In this case, enter OldandNew

Then Click on OK

Graph > Dotplot> Multiple Ys Simple

Another useful graphical tool is the .

Enter the columns to be

In this case, enter


Another useful graphical tool is the .

Enter the columns to be

In this case, enter


84


Dotplots (2)

The Dotplot is similar to a Histogram, because it helps toshow the distribution of data groups.

In this case, the two Dotplots enable the variation in twoor more groups to be examined side by side.

Data

12.9612.9412.9212.9012.8812.86

Old

New

Dotplot of Old, New


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Graph Editing Tools (1) EditingToolbar

Put the activegraph incrosshairsmode

Select a graphitem for editing.

Access the editingdialogue box for theselected item

Put the activegraph in selectmode

Put the activegraph in brushmode

Delete theselected item

Select a graphitem to add

Make the graph

appear largeror smaller usingzoom option

Put the active

crosshairsmode

item for editing.



Put the activegraph in brushmode


item to add

Make the graph


item for editing


Put the active

mode

Put the active

mode


item to add

Make the graph


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Graph Editing Tools (2) AnnotationToolbar

Draw a polyline (aseries ofconnecting lines)

on a graph


Add text to agraph

Draw rectangles orsquares on a graph

Draw ellipses orcircles on a graph

Draw lines on agraph

Add markersymbols on a

graph

Draw a polygonon a graph

Draw a polyline (aseries ofconnecting lines)

on a graph


Add text to agraph





graph



Add text to agraph





graph



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Analysing the Data using Graphs -SummaryThe Scatterplot was used to compare the Newand Oldprocesses.

Basic Statistics were used to confirm differences in key statistics such as themean (average) and standard deviation (variation).

The Histogram provided a visual check of the shape of the distribution ofeach process (data set).

Times Series Plots were used to check for trends over time.

A Boxplot was used to compare the Newand Oldprocesses against each

other, and the results were also stratified into different time sections.

The Dotplot was used to confirm information from previous graphs.

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Data Analysis Group Exercise Page 1

1. Open the worksheet, poplar1.mtw

2. Add the following data to the bottom of the existing columns:

Diameter Height Weight

1.52 2.9 0.07

4.51 5.27 0.79

1.18 2.2 0.03

3.17 4.93 0.443.33 4.89 0.52

3. Create a new column variable that indicates whether an observation was taken from a site with rich,

well drained soil (1), or a site with dry, sandy soil (2). Create a Variable called sitecontaining ten 1sfollowed by ten 2s.

4. Produce a separate summary table for each of the 3 variables, stratified by sitetype. Create

Boxplots & Dotplots of the three variables stratified by sitetype.

What do the descriptive data and the graphs tell you?


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Data Analysis Group Exercise Page 2

5. Researchers have discovered that the weight of the tree is closely related to thesquare of diameter, multiplied by height.

Create a new column called D2Hcontaining the above calculation, using Minitabscolumn calculator.

6. Create a Scatterplot to see if there is a relationship between weight and the newvariable D2H.

What does the Scatterplot tell you?

Is there any unusual data?

7. Do a normality test on the two variables (weight & D2H).

What does the Normality Test tell you?

8. Produce Histograms of the Variables, Weight and D2H.

What do they tell you?

02 Introduction to Minitab

Documents

Transcript of 02 Introduction to Minitab