You can adjust the "Percentage Base" by selecting Edit Settings in Crosstabs. By default, the drop down menu on the right allows you to select one of the following:
- Total Answering (default)
- Total Shown
- Total in Segment
However, you may wish to show the percentage calculation based on the number of respondents who were shown a specific answer option in the multi-select question, rather than the entire question. Consider the following example:
<checkbox label="Q2" atleast="1" rowcond="Q1[row]"> <title>Select all that apply:</title> <row label="r1">Item 1</row> <row label="r2">Item 2</row> <row label="r3">Item 3</row> <row label="r4">Item 4</row> </checkbox> <suspend/>
In this example, the rows at Q2 are shown only if they're selected at Q1. If 3 out of the total 4 respondents selected r3, then the percentage would be 75% for r3 at Q2. However, if only 3 people actually saw r3, then that would mean 3 out of the total 3 respondents who saw r3 selected r3, which is 100%.
2: Percentages Based on Individual Checkboxes
To show the percentage calculations base based on individual checkboxes, we can add
trackVars="checkbox" to the project's <survey> tag.
<?xml version="1.0" encoding="UTF-8"?> <survey name="Survey" ... ... trackVars="checkbox" ...>
In doing so, a new option, "Total Shown Variable", will be available in the percentage base drop down menu:
Selecting "Total Shown Variable" will adjust the percentage calculations for <checkbox> questions to base the number on the total number of respondents who saw the individual checkbox selection rather than the question as a whole.
2.1: Control trackVars at the Question Level
Use the tv attribute to control how
trackVars works at the question level. For example:
<checkbox label="Q10" atleast="1" tv="off">
tv="auto" is specified and
trackVars will work normally.
tv="off" is specified, then
trackVars will not take effect at this question. This means that the question's data values will only be blank if the question was skipped altogether.
tv="force" is specified, then all of the question's cells will be considered to have been seen. If new rows are later added and merged in, those rows will be marked as unseen.