1 Business 90: Business Statistics Professor David Mease Sec 03, T R 7:30-8:45AM BBC 204 Lecture 8 =...

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Business 90: Business Statistics

Professor David Mease

Sec 03, T R 7:30-8:45AM BBC 204

Lecture 8 = Finish Chapter “Presenting Data in Tables and Charts”

(PDITAC)

Agenda:1) Go over quiz on Homework 22) Reminder about Homework 3 (due Tuesday)3) Lecture over rest of Chapter PDITAC

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Homework 3 - Due Tuesday 2/23 1) The dataset at http://www.cob.sjsu.edu/mease_d/sec4lettergrades.xls gives the letter grades for a quiz I gave once.

a) Make a summary table for the letter grades using the PivotTable in Excel. In your summary table list the grades in the order A+, A, A-, B+, etc. Double check a few of your answers by hand.

b) Make the bar chart using Excel with the grades in the same order as in part A.

c) Make the pie chart using Excel.

d) Make the pareto diagram using Excel.

2) The dataset http://www.cob.sjsu.edu/mease_d/America_West_Flights.xls contains flight status information for America West flights departing from four major West Coast airports. Make a contingency table for this data using the PivotTable feature in Excel.

3) Do textbook problem number 48 in Chapter “Presenting Data in Tables and Charts”.

4) The dataset at http://www.cob.sjsu.edu/mease_d/gpa-data.xls contains data from 20 San Jose State University graduating seniors who were asked to report their high school GPA (first column) and their current college GPA (second column).

a) Make a scatter plot of this data with High School GPA on the X-axis and College GPA on the Y-axis using Excel.

b) Give the equation of the least squares regression line using Excel.

c) What is the slope of the least squares regression line?

d) Interpret the slope of the least squares regression line.

e) What is the coefficient of correlation?

f) What is the value of R-squared?

g) Use the least squares regression line to predict the college GPA of a student who had a high school GPA of 2.7.

Important: Again, be sure to print out your solutions and bring them with you to class for the quiz.

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Presenting Data in Tables and Charts

Statistics for ManagersUsing Microsoft® Excel

4th Edition

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Chapter Goals

After completing this chapter, you should be able to: Create an ordered array Construct and interpret a frequency distribution,

histogram, and polygon for numerical data Construct and interpret a cumulative percentage

distribution and ogive for numerical data Create and interpret contingency tables, bar charts,

and pie charts for categorical data Create and interpret a scatter diagram and a least

squares regression line (in other chapter p. 387-398) Describe appropriate and inappropriate ways to

display data graphically

http://www.sjsu.edu/

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Graphs and Tables for Two Variables (Bivariate Data)

Two Numerical Variables:

Scatter Diagram

Two Categorical Variables:

Contingency Table (also called cross-classification table or two-way table)

Side-by-Side Bar Chart


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Contingency Tables Using Excel

Just like with summary tables, to make a contingency table in Excel, it is often useful to use a “Pivot Table” to count the frequencies of the different categories, especially for large datasets. This is done by selecting “Data” and then “PivotTable and PivotChart Report”. Next go to “Layout” and drag the name of one variable into the row and the other into the column. Pick either one and also drag it into the data area. (Be sure you name the two columns where you have the data first.)


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In class exercise #25:The file http://www.cob.sjsu.edu/mease_d/gender_and_major.xls lists the genders and majors for Bus 90 students from a previous term. Make a contingency table using the Pivot Table feature in Excel. Put Gender along the side and major along the top.

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In class exercise #25:The file http://www.cob.sjsu.edu/mease_d/gender_and_major.xls lists the genders and majors for Bus 90 students from a previous term. Make a contingency table using the Pivot Table feature in Excel. Put Gender along the side and major along the top.

ANSWER: MajorGender Business Non-Business UndeclaredFemale 49 6 2Male 48 13 2

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Scatter Diagram




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In class exercise #26:Make a side-by-side bar chart for the data from ICE #25 by hand. Put the major along the x-axis and use different colored bars for the two genders.

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In class exercise #26:Make a side-by-side bar chart for the data from ICE #25 by hand. Put the major along the x-axis and use different colored bars for the two genders.

ANSWER:Gender and Major

0

5

10

15

20

25

30

35

40

45

50

Business Non-Business Undeclared

Major

Fre

qu

ency

.

.

Female

Male

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Scatter Diagram




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Scatter Diagrams are used for bivariate numerical data Bivariate data consists of paired

observations taken from two numerical variables

The Scatter Diagram: one variable is measured on the vertical

axis and the other variable is measured on the horizontal axis

Scatter Diagrams

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Scatter Diagram Example

Cost per Day vs. Production Volume

0

50

100

150

200

250

0 10 20 30 40 50 60 70

Volume per Day

Cos

t per

Day

Volume per day

Cost per day

23 125

26 140

29 146

33 160

38 167

42 170

50 188

55 195

60 200

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Scatter Diagrams in Excel

Select “Insert” > “Chart”

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2Select XY(Scatter) option,

then click “Next”

The data range is the y values and the x values go under the “Series” tab

Important: Don’t include column names

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In class exercise #27:The file http://www.cob.sjsu.edu/mease_d/football.xls gives the total number of wins for each of the 117 Division 1A college football teams for the 2003 and 2004 seasons. Use Excel to make a scatter diagram for this data. Put 2003 wins on the x-axis.

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In class exercise #27:The file http://www.cob.sjsu.edu/mease_d/football.xls gives the total number of wins for each of the 117 Division 1A college football teams for the 2003 and 2004 seasons. Use Excel to make a scatter diagram for this data. Put 2003 wins on the x-axis.

ANSWER:

Football

0

2

4

6

8

10

12

0 2 4 6 8 10 12

2003 Wins

2004

Win

s

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Described on pages 387-398 (in a different chapter)

It is the line that fits the data the best as determined by minimizing squared vertical differences

The coefficient of correlation (r) measures the strength and direction of the linear relationship (positive=up, negative=down)

R-squared also measures the strength of the linear relationship, but not the direction

The Least Squares Regression Line

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Scatter Plots of Data with Various Correlation Coefficients

Y

X

Y

X

Y

X

Y

X

r = -1 r = -.6

r = +.3r = +1

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Adding the Least Squares Regression Line Using Excel

Click once on the graph1

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From the “Chart” menu select “Add Trendline”2

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Choose the first choice (“Linear”) and press “OK”3

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Adding the Least Squares Regression Line Using ExcelThe line should now appear on your scatter diagram. Double click on the line then under the “Options” tab check the last two

boxes.4

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In class exercise #28:A) Graph the least squares regression line for the football data on the scatter diagram using Excel.

B) Give the equation of the least squares regression line using Excel.

C) What is the slope of the least squares regression line?

D) Interpret the slope of the least squares regression line.

E) What is the coefficient of correlation?

F) What is the value of R-squared?

G) Use the least squares regression line to predict the number of 2004 wins for a team that won 12 games in 2003.

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In class exercise #28:A) Graph the least squares regression line for the football data on the scatter diagram using Excel.

ANSWER for Part A:

Football Data

y = 0.5716x + 2.1623

R2 = 0.4274

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2

4

6

8

10

12

0 2 4 6 8 10 12

2003 Win Total

2004

Win

Tot

al

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Principles of Graphical Excellence

Present data in a way that provides substance, statistics and design

Communicate complex ideas with clarity, precision and efficiency

Give the largest number of ideas in the most efficient manner

Excellence almost always involves several dimensions

Tell the truth about the data

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Using “chart junk” Failing to provide a relative

basis in comparing data

between groups Compressing or distorting the vertical axis Providing no zero point on the vertical axis

Errors in Presenting Data

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Compressing Vertical Axis

Good Presentation

Quarterly Sales Quarterly Sales

Bad Presentation

0

25

50

Q1 Q2 Q3 Q4

$

0

100

200

Q1 Q2 Q3 Q4

$

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No Zero Point On Vertical Axis

Monthly Sales

0

39

42

45

J F M A M J

$

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0

20

40

60

J F M A M J

$

Good Presentations

Monthly Sales

Bad Presentation

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39

42

45

J F M A M J

$

Graphing the first six months of sales

or

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No Relative Basis

Good PresentationA’s received by

students.A’s received by

students.

Bad Presentation

0

200

300

FR SO JR SR

Freq.

10%

30%

FR SO JR SR

FR = Freshmen, SO = Sophomore, JR = Junior, SR = Senior

100

20%

0%

%

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Chart Junk

Good Presentation

1960: $1.00

1970: $1.60

1980: $3.10

1990: $3.80

Minimum Wage Minimum Wage

0

2

4

1960 1970 1980 1990

$

Bad Presentation

1 Business 90: Business Statistics Professor David Mease Sec 03, T R 7:30-8:45AM BBC 204 Lecture 8 =...

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