Calculating Percentages

We regularly receive requests from people who are puzzling over the graphs in Blackboard’s Enterprise Survey tool. They are interesting because they show the bars stacked horizontally, rather than as a normal bar chart. They also display a measure of average as a percentage rather than a mean (which isn’t daft as the range of possible values of the mean grows as the number of Likert options increases).
To help you convert between percentages and means (and understand how they are calculated) we have produced the following worked examples as a PDF and Excel.

Note these files were updated in February 2017 and supersede any previous versions which should be disguarded.

Worked Example (PDF)

 Enterprise Survey Convertor

If you want to bulk convert a lot of percentages to means, use the Excel formula given at the end of the PDF or the Conversion Tables tab on the worksheet. There are also worked examples for 4, 5 and 6 point Likerts.

 Note there is also a bug in Blackboard relating to the percentages.
It only affects questions that meet both these criteria:

  1. The question is a likert question which has a ‘Not Applicable’ option
  2. The question is deployed as part of a matrix.

The bug does not affect standard Likert questions with a ‘Not Applicable’ option – it only affects those deployed as a matrix.
In affected questions, Blackboard incorrectly includes the number of ‘Not Applicable’ responses when calculating the mean value. Until this bug is fixed, to get the correct percentage you will need to feed the results into the appropriate 4 Point Likert, 5 Point Likert or 6 Point Likert tab on the worksheet.