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Graphing Data. Graphing Data. Frequency Distributions. Graphing Data. Frequency Distributions Each value of interest listed on the x-axis Best suited when variable has small, finite number of possible values What types of variables fit this definition?. Graphing Data. - PowerPoint PPT Presentation

### Transcript of Graphing Data

• Graphing Data

• Graphing DataFrequency Distributions

• Graphing DataFrequency DistributionsEach value of interest listed on the x-axisBest suited when variable has small, finite number of possible values

What types of variables fit this definition?

• Graphing DataStem-and-Leaf Displays

• Graphing DataStem and leaf displaysStem = Leading Digit = Most Significant DigitLeaf = Trailing Digit = Least Significant DigitUnlike frequency distribution, can reconstruct entire raw data set very easilyStem is typically tens digit (Xx), but can be hundreds (Xxx) if all values are 100+ or the thousands (Xxxx) if all values are 1,000+Bad if we have many of our values under one stem

• Graphing DataStem-and-Leaf Displays

• Graphing DataStem-and-Leaf DisplaysBDI2TOT Stem-and-Leaf Plot Frequency Stem & Leaf28.00 0 * 000000000000000011111111111125.00 0 t 222222222222333333333333323.00 0 f 4444444444445555555555530.00 0 s 66666666666666666677777777777722.00 0 . 888888888889999999999917.00 1 * 0000000111111111118.00 1 t 22222222222333333314.00 1 f 444444445555559.00 1 s 66666777718.00 1 . 8888888899999999996.00 2 * 0001112.00 2 t 336.00 2 f 4455554.00 2 s 66772.00 2 . 881.00 3 * 12.00 3 t 2211.00 Extremes (>=35)Stem width: 10Each leaf: 1 case

• Graphing DataPut the following data in a stem and leaf plot using the *, t, f, s, . system

• Graphing DataHistogramsBars represent certain interval in this case 10 units1st bar = 0-10, 2nd bar = 11-20, etc.Best for data that fall into intervals naturally, i.e. discrete, categorical, nominal or sometimes ordinal variables

• Graphing DataHistogramsWhen choosing graph intervals, only rule is to maximize quick readabilityOutlier

• Graphing DataHistograms2nd bar = 11-20In practice though, a score of 10.5 would be rounded to 11, and a score of 20.4 to 20, and so our actual range is from 10.5 20.4these are called the real upper limits and the real lower limits11-20 = upper and lower limits 10.5-20.4 = real upper and lower limits

What are the real limits for our 3rd bar (21-30)?

• Graphing DataLine GraphsBest for when data continuous, dimensional, or on interval or ratio scalesSame as previous histogram, but provides much richer information if this information is meaningful, use a line graph if its just noise, use a bar graph

• Graphing Data

• Graphing Data

Chart1

51211

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101725

6415

3311

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Sheet1

5710632

121517432

11132515117

Sheet1

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Sheet3

• Graphing DataWays to Describe a Graph:Symmetry

Modality

Skewness

Kurtosis

• Graphing DataWays to Described a Graph:Symmetry (the graph below is Symmetric)

• Graphing DataWays to Described a Graph:Modality (the graph below is Bimodal)

• Graphing DataWays to Described a Graph:Skewness (the graph below is Right/Positively Skewed, and hence Non-symmetric)

• Graphing DataWays to Described a Graph:Kurtosis

• Graphing DataWays to Described a Graph:Kurtosis

• Graphing DataWays to Described a Graph:Kurtosis