D:\687320605.doc
Page 1 of 3
USING SPSS FOR WINDOWS TO OBTAIN z SCORES AND
PERCENTILES
z scores
In SPSS for WINDOWS, z scores are obtained through the DESCRIPTIVES
procedure, and percentiles through the FREQUENCIES procedure:
Here are some scores to use to demonstrate z scores and percentiles:
EXPERIMENTAL GROUP: 85,90,82,75,99
CONTROL GROUP: 70,66,52,71,50
_____ 1. Open SPSS for Windows, enter the scores, and name the variables as usual:
_____ 2. Click on Statistics (or Analyze), Descriptive Statistics, and Descriptives.
_____ 3. When the Descriptives box opens, move the score variable from the left side to
the right side by highlighting its name on the left side, then clicking the RIGHT ARROW
button in the middle of the box.
_____ 4. Put a checkmark in the checkbox labeled Save Standardize Values as
Variables.
_____ 5. Click the options button and choose the statistics you want (your choice).
_____ 6. Click the Continue button.
D:\687320605.doc
Page 2 of 3
_____ 7. Click the OK button, and the analysis will run.
_____ 8. If you are not returned to the data screen, return to it by clicking the unselected
SPSS icon at the bottom of the screen.
_____ 9. On the data screen, you will see the z scores for each of the variables in a new
column headed zscore. (Remember that these z scores are calculated for the entire 10
scores, not for each group separately.)
_____ 10. Print out both the data screen, and the output screen.
Percentiles
To obtain the 30th percentile, use the FREQUENCIES procedure:
_____ 1. Return to the data screen if you are not already there.
_____ 2. Click on Analyze, Descriptive Statistics, and Frequencies.
_____ 3. Highlight the score variable on the left and move it to the right field by clicking
the RIGHT ARROW button in the middle of the box.
_____ 4. Click the Statistics button.
_____ 4. When the Frequencies: Statistics box appears, put a check in the percentiles
box and type in 30 (in order to get the point in the distribution of the score variable that is
at the 30th percentile).
_____ 5. Click the Add button to add the percentile to list of percentiles you want. (YOU
CANNOT SKIP THIS STEP.)
_____ 6. Put checks next to the other statistics you want.
_____ 7. Click Continue and then OK.
_____ 8. SPSS for WINDOWS will run your statistics, which you will now see. Among
other things, you will find the point on the scale that represents the 30th percentile in the
Statistics section of the output:
(GO ON TO THE NEXT PAGE)
D:\687320605.doc
Page 3 of 3
_____ 9. So, the 30 percentile is at the point on the scale at a score of 67.2.
_____ 10. Print out the output screen and circle the percentile.
TURN IN ALL THREE PRINTOUTS STAPLED TOGETHER. BE SURE
YOUR NAME IS ON ALL SHEETS. LABEL THE FIRST PAGE AS:
"SPSS FOR WINDOWS z SCORE AND PERCENTILE
ASSIGNMENT."