1. Organizing Qualitative Data
Chapter 2 Section 1
Organizing
Qualitative Data

2. Chapter 2 – Section 1 Learning objectives
Organize qualitative data in tables
Construct bar graphs
Construct pie charts 1 2 3

3. Chapter 2 – Section 1 Learning objectives
Organize qualitative data in tables
Construct bar graphs
Construct pie charts 1 2 3

4. Chapter 2 – Section 1
Raw qualitative data comes as a list of values … each value is one out of a set of categories
These values can be organized as either a long list or in a table
Interpreting the list of data can be difficult, particularly if there is a lot of data
Methods are needed to aid interpretation
Raw qualitative data comes as a list of values … each value is one out of a set of categories
These values can be organized as either a long list or in a table

5. Chapter 2 – Section 1
Qualitative data values can be organized by a frequency distribution
A frequency distribution lists
Each of the categories
The frequency for each category

6. blue, blue, green, red, red, blue, red, blue
Chapter 2 – Section 1
A simple data set is
blue, blue, green, red, red, blue, red, blue
A frequency table for this qualitative data is
The most commonly occurring color is blue
Color
Frequency
Blue 4
Green 1
Red 3

7. Chapter 2 – Section 1
The frequencies are the counts of the observations
The relative frequencies are the proportions (or percents) of the observations out of the total
A relative frequency distribution lists
Each of the categories
The relative frequency for each category
The frequencies are the counts of the observations
The frequencies are the counts of the observations
The relative frequencies are the proportions (or percents) of the observations out of the total

8. blue, blue, green, red, red, green, blue, blue
Chapter 2 – Section 1
Use the same simple set of data
blue, blue, green, red, red, green, blue, blue
A relative frequency table is computed as follows
Sum of all frequencies = 8 (there are 8 observations)
Blue has a relative frequency of 4 / 8 = .500
Green has a relative frequency of 1 / 8 = .125
Red has a relative frequency of 3 / 8 = .375

9. Chapter 2 – Section 1
A relative frequency table for this qualitative data is
A relative frequency table can also be constructed with percents (50%, 12.5%, and 37.5% for the above table)
Color
Relative Frequency
Blue
.500
Green
.125
Red
.375

10. Chapter 2 – Section 1
Tables are useful because they provide an exact count for the data
However, if the data set is medium to large in size, it may be difficult to understand the data when presented in a table
Additional techniques are needed to give a better idea of “the big picture”

11. Chapter 2 – Section 1 Learning objectives
Organize qualitative data in tables
Construct bar graphs
Construct pie charts 1 2 3

12. Chapter 2 – Section 1
In general, pictures of data send a more powerful message than tables
Visual methods, such as bar graphs, present a better summary than just a table
A bar graph
Lists the categories on the horizontal axis
Draws rectangles above each category where the heights are equal to the category’s frequency or relative frequency
In general, pictures of data send a more powerful message than tables
Visual methods, such as bar graphs, present a better summary than just a table

13. Chapter 2 – Section 1 Bar graphs for our simple data (using Excel)
Frequency bar graph
Relative frequency bar graph

14. Chapter 2 – Section 1 Good practices in constructing bar graphs
The horizontal scale
The categories should be spaced equally apart
The rectangles should have the same widths
The vertical scale
Should begin with 0
Should be incremented in reasonable steps
Should go somewhat, but not significantly, beyond the largest frequency or relative frequency
Good practices in constructing bar graphs
The horizontal scale
The categories should be spaced equally apart
The rectangles should have the same widths

15. Chapter 2 – Section 1 A Pareto chart is a particular type of bar graph
A Pareto differs from a bar chart only in that the categories are arranged in order
The category with the highest frequency is placed first (on the extreme left)
The second highest category is placed second
Etc.
Pareto charts are often used when there are many categories but only the top few are of interest
A Pareto chart is a particular type of bar graph
A Pareto differs from a bar chart only in that the categories are arranged in order
The category with the highest frequency is placed first (on the extreme left)
The second highest category is placed second
Etc.

16. Chapter 2 – Section 1
A Pareto chart for our simple data (using Excel)

17. Chapter 2 – Section 1 An example with more data values
A data set from the text
Even with only 30 data values, this table cannot be interpreted easily

18. Chapter 2 – Section 1 Graphs for this set of data
A frequency bar graph
A relative frequency bar graph
These graphs are more effective than the table

19. Chapter 2 – Section 1
Graphs for this data (continued)
A Pareto chart

20. Chapter 2 – Section 1
Two qualitative variables can be compared by comparing their bar graphs
A side-by-side bar graph draws two rectangles for each category, one for each variable
The frequencies (or relative frequencies) for each category can be compared

21. Chapter 2 – Section 1
An example side-by-side bar graph comparing educational attainment in 1990 versus 2003

22. Chapter 2 – Section 1 Learning objectives
Organize qualitative data in tables
Construct bar graphs
Construct pie charts 1 2 3

23. Chapter 2 – Section 1
A pie chart is a circle divided into sections, one for each category
The area (angle) of each sector is proportional to the frequency of that category
Pie charts are useful to show the relative proportions of each category, compared to the whole

24. Chapter 2 – Section 1 Good practices for constructing pie charts
Different colors should be used to distinguish the categories
Each category should be labeled with the category name and relative frequency
Pie charts are not as effective if there are too many categories or if some relative frequencies are too small
Good practices for constructing pie charts
Different colors should be used to distinguish the categories
Each category should be labeled with the category name and relative frequency

25. Chapter 2 – Section 1
An example of a pie chart for the 2003 data from the side-to-side bar chart

26. Chapter 2 – Section 1
Side-by-side pie charts are used sometimes, but can be difficult to interpret (using Excel, with substantial modifications)

27. Summary: Chapter 2 – Section 1
Qualitative data can be organized in several ways
Tables are useful for listing the data, its frequencies, and its relative frequencies
Charts such as bar graphs, Pareto charts, and pie charts are useful visual methods for organizing data
Side-by-side bar graphs are useful for comparing two sets of qualitative data