How To Compute Percentiles
Q's Histogram tool can be used to generate a new question which groups respondents by the percentiles of a Number question. This new question can be used to show the percentile scores for the original Number question.
Creating Categories for Percentiles
This example considers quartiles (i.e. 25th, 50th, 75th percentiles), but other percentiles can be generated by changing the number of categories specified.
- Create a table with the Number question selected in the Blue drop-down menu, and SUMMARY selected in the Brown.
- Select Show Data As and choose Histogram.
- Below the histogram, select Create Categories.
- Change the number of Categories to 4. This number is appropriate for quartiles. For deciles (10th, 20th, 30th, etc. percentiles) instead enter 10. Or, manually drag the red lines about to create any percentile of interest.
- Select Make Equal Proportions.
- Make a new table.
- Show the new question called Histogram Categories - <Your question name> in the Blue drop-down menu. This question is generated at the time you create categories from the Histogram.
- Rename the labels:
- 25th Percentile
- 50th Percentile
- 75th Percentile
- 100th Percentile
The categories of the question contain respondents in the percentiles of the original question.
This question depends upon the histogram, so do not remove or modify the histogram further.
Showing Percentile Scores
To show the percentile scores:
- Show the new Histogram Categories - <Your question name> question in the Blue drop-down menu.
- Show the original Number question in the Brown drop-down menu.
- Right-click on the table and select Statistics - Cells > Maximum.
As the definition of percentiles is ambiguous these numbers may differ slightly to those shown by the results for 5th Percentile, 25th Percentile, 75th Percentile, and 95th Percentile in the Statistics - Cells.