Chapter 2 Frequency Distributions

1. Chapter 2Frequency Distributions

2. Ranked Frequency Distributions Order raw data by listing so that the highest number is at the top and the lowest number is at the bottom.

3. Ranked Frequency DistributionExample Raw Data 3 8 6 9 5 2 7

4. Simple Frequency Distributions Created by listing all possible score values in any distribution and then indicating the frequency (f).

5. Simple Frequency DistributionExample Raw Data

6. Grouped Frequency Distributions Raw data are combined into equal-sized groups called class intervals.

7. Constructing the Class Intervals:How Big and How Many? • First compute the range, the full extent of scores from the highest to the lowest score. Range = high score – low score

8. Constructing Class Intervals (con’t) • Next, select an interval size (i). • Choose an interval sizethat produces between 10 and 20 intervals.

9. Constructing the Class Intervals and Determining Frequency • Each class interval is represented by a lower limit and an upper limit. • Each class interval is the same size. • The top interval must contain the highest score. • The bottom interval must contain the lowest score. • Establish a lower limit that is a multiple of the interval size.

10. Grouped Frequency DistributionExample Range = 49 – 1 = 48

13. Midpoint

14. Cumulative Frequency (CF) Total number of scores that fall below the upper real limit of an interval. Helpful when you need to know how many scores in a distribution fall below a particular score.

15. n

16. Relative Frequency The proportion of scores from the distribution that fall within the real limits of an interval.

17. Sum of relf = n

18. Cumulative Relative Frequency The total proportion of scores that lie below the upper real limit of the interval.

20. Cumulative Percent or Percentile Multiply the cumulative relative percent X 100