Setting an Answer Option Base to Total Shown

1:  Overview

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 participants 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 participants 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 participants 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.

Note: Surveys with delphi="1" have this attribute on by default.

<?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 participants 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">

By default, tv="auto" is specified and trackVars will work normally.

If 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.

If 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.

If the question has where="execute", trackVars is implicitly set to off. To track a question with where="execute", set tv to tv="record". This will decrease performance if you have many records. On a question without where="execute", using tv="record" is the same as using tv="off".

3:  What's Next?

Learn more about other options for Configuring Crosstab Settings.

The trackVars attribute is one of many Survey Tag attributes.