Section 2.2 | Grouped Frequency Distribution Tables

Question 1

What is a grouped frequency distribution table?

Answer 1

The goal of tables is to present a relatively simple, organized picture of the data. Data that has a wide range would produce a cumbersome table. A grouped frequency distribution table presents data as groups of scores rather than individual values. The groups, or intervals, are called class intervals.

Question 2

What four guidelines should you abide by when making grouped frequency distribution tables?

Answer 2

1. The grouped frequency distribution table should have about 10 class intervals. You may have more or less than 10 depending on your needs and situation, but the goal is always to present a table that is relatively easy to see and understand.
2. The width of each interval should be a relatively simple number; for example, 2, 5, 10, or 20.
3. The bottom score in each class interval should be a multiple of the width.
4. All intervals should be the same width, with no gaps or overlaps.

Question 3

What are apparent limits and how do they apply to frequency distributions?

Answer 3

The concept of real limits applies to the class intervals of a grouped frequency distribution table. For example, a class interval of 40-49 contains scores from X=40 to X-49. These values are called apparent limits of the interval because it appears that they form the upper and lower boundaries for the class interval.

The real limits are actually 39.5 (real lower limit) and 49.5 (real upper limit), since 40 has a lower limit of 39.5 and 49 has an upper limit of 49.5. The distance between these two real limits (10 points) is the width of the interval.