Convert Raw Scores to Cumulative Percentages
Step 3: Compute the Cumulative Frequency.
The next step is to compute the cumulative frequency (cf). In order to do this, look at the numbers that were entered into the frequency (f) column and add them up. 2+7+3+1+2=15. This will give you the number of scores that are at or below the X value of 99. Place the number 15 in the column labeled cf. (Note: The highest score in the X column will equal cf=∑f. In this case, cf=∑f corresponds to X=99. Because all of the scores in the distribution are at or below X=99; X=99 also corresponds to the 100th percentile.)
To determine the cumulative frequency (cf) of X=80, add together the numbers in the f column beneath 7 and include 7. For example, add 7+3+1+2=13. Record 13 in the cf column across from X=80.
Next find the cumulative frequency (cf) for X=60. Now you will add together 3+1+2=6. Record 6 in the chart below cf across from X=60.
Next, find the frequency of X=59. In order to do this, add 1+2=3 and enter 3 in the column under cf across from X=59.
Next, find the frequency of X=25. X=25 occurs 2 times. Therefore, the frequency of X=25 is 2. Record 2 in the column under cf across from X=25.
Copyright 2005 by the Student Success Center and the University of Houston-Victoria.
Created 2004 by Maranda Koenig. Content Reviewed by Hari Damodaran. Edited by Sandra Heinold.