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3.2.4 Known-groups comparison
Known-groups validity is being demonstrated
whenever a test or questionnaire can realistically
discriminate between two groups that are known to differ
on the variable of interest (Davidson, 2014). A
known-groups comparison can be performed to validate
an individual item or a set of questions (or otherwise
termed as a domain). A question or domain is considered
valid if the two populations of specific and distinctly
different characteristics appear to have significant
differences in their mean or median score. An example is
shown in Figure 3.4. The result shows that the two
different groups namely “Healthy individuals” and
“Patients receiving treatment in a psychiatric clinic”
reported different mean scores for distress which was
measured by using the K10 questionnaire. (Tiong et al.,
2018). Thus, the K10 questionnaire is useful for
