Chapters 2
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2. Chapters 2 & 3 (Part A) Descriptive Statistics: Tabular and Graphical Presentations Summarizing Qualitative Data
Summarizing Quantitative Data
3. Summarizing Qualitative Data Frequency Distribution
Relative Frequency Distribution
Percent Frequency Distribution
Bar Graph
Pie Chart
4. Construction of a Frequency Distribution
6. Example: Marada Inn Guests staying at Marada Inn were
asked to rate the quality of their
accommodations as being excellent,
above average, average, below average, or
poor. The ratings provided by a sample of 20 guests are:
9. Percent Frequency Distribution
11. Bar Graph
13. Pie Chart
16. Summarizing Quantitative Data Frequency Distribution
Relative Frequency and Percent Frequency Distributions
Dot Plot
Histogram
Cumulative Distributions
Ogive
17. 1- Determine range
2- Select number of classes
Usually between 5 and 20 inclusive
3- Compute class intervals (width)
4- Determine class boundaries (limits)
5- Compute class midpoints
6- Count observations & assign to classes Frequency Distribution Table Steps
18. Example: Hudson Auto Repair
20. Frequency Distribution Guidelines for Selecting Number of Classes
21. Frequency Distribution (Continued) Guidelines for Selecting Width of Classes
22. Example: Frequency Distribution For Hudson Auto Repair, if we choose six classes:
23. Solution Using SWStat+ After putting your data into Excel, then create Data Area:
24. SwStat Statistics Tabulations and Histograms
Note that here we are using 10 classesyou can use 6 classes if you would like to do so.
Solution Using SWStat (cont.)
25. Results: Solution Using SWStat (cont.)
26. Relative Frequency and Percent Frequency Distributions
28. Dot Plot One of the simplest graphical summaries of data is a dot plot.
A horizontal axis shows the range of data values.
Then each data value is represented by a dot placed above the axis.
29. Dot Plot
30. Histogram
31. Histogram
32. Symmetric
Left tail is the mirror image of the right tail
Example: heights and weights of people Histogram (Continued)
33. Moderately Skewed Left
A longer tail to the left
Example: exam scores Histogram (Continued)
34. Moderately Right Skewed
A Longer tail to the right
Example: housing values Histogram (Continued)
35. Highly Skewed Right
A very long tail to the right
Example: executive salaries Histogram (Continued)
37. Cumulative Distributions Example: Hudson Auto Repair
41. Frequency Distribution Table Another Example
42. Frequency Distribution Table Example (Continued)
45. Relative Frequency & % Distribution Tables Example (Continued) The number of classes is usually between 5 and 15. Only 3 are used here for illustration purposes.The number of classes is usually between 5 and 15. Only 3 are used here for illustration purposes.
46. Cumulative Percentage Distribution Table Example (Continued) The number of classes is usually between 5 and 15. Only 3 are used here for illustration purposes.The number of classes is usually between 5 and 15. Only 3 are used here for illustration purposes.
47. End of Chapters 2 & 3, Part A