What is test-retest reliability?
Reliability can take different forms in psychometric assessment. In the case of ‘test-retest’, reliability means the extent to which Strengthscope® consistently reports a similar pattern of strengths for the same respondent over time. In other words, the temporal stability of the assessment.
Why does test-retest reliability matter when choosing psychometric assessments?
When you complete a psychometric assessment, you expect it to be accurate. Accuracy can be assessed in terms of validity (how accurately an assessment describes a person with respect to the areas it covers, like personality, ability or career preferences for example).
Accuracy can also be assessed in terms of reliability (how consistently an assessment measures a person over time and situation).
It’s important to know that if an assessment’s reliability is low, this also affects its validity. Therefore, reliability is an extremely important aspect of the accuracy of an assessment’s results.
Publishers of psychometric assessments should be transparent in providing information relating to the reliability of their profiles. The majority do provide information relating to test-retest reliability, but as a buyer or user, you may need to ask.
It’s also important to know that the test-retest reliability of assessments in the market varies significantly. The British Psychological Society’s test registration process requires a minimum test-retest reliability criterion of 0.7 (on a scale of 0.0-1.0) for any constructs (e.g. strengths or personality characteristics) measured by an assessment.
However, many assessments fall short of this criterion for some, or even most, of the constructs they measure. And for others, their test-retest reliability falls sharply after a relatively short period of time… say a few weeks or months. This means that if you were to retake such an assessment with a year’s time gap, you might get slightly, or even entirely, different results.
A rule of thumb in the psychometrics industry is that, due to test-retest reliability limitations, you should recomplete most assessments after a maximum of two years. For many assessments, it should be sooner. And for some, specifically those that are most affected by context and situation, there should be no expectation of consistency over time, as results can be affected by external variables, and so each testing occasion should be treated as a ‘one off’ (test publishers are usually clear when this is the case).
What is Strengthscope’s reliability?
Strengthscope® is registered with the British Psychological Society and has been rigorously tested to check how consistent results are over time. In our test registration results from the British Psychological Society, Strengthscope® achieved well above the expected criterion for test-retest reliability across all 24 strengths for a time gap of 1 year.
Since achieving test registration status, we have continued to research Strengthscope®’s test-retest reliability. In our database today are people who completed with a 1-year gap, as well as those with 2-, 3-, 4-, and more years between completions.
Compared with the industry standard of two years before re-completing, Strengthscope® holds up well. Our research shows that Strengthscope® results remain stable for four years, and longer in many cases. After four years, the reliability starts to reduce marginally, and so it may make sense to recomplete the Strengthscope® assessment after this time period.
What is our advice on recompleting Strengthscope®?
It is important to say that despite Strengthscope®’s strong overall test-retest reliability credentials, strengths, especially your Significant 7, can change sooner in some situations. You may want to retake Strengthscope® within 4 years if:
- You have had a major role, career or life change that affects what you enjoy at work
- You have intentionally changed how you use certain strengths because your context has changed, for example using one less often or relying on another more.
Explore more of the science and research behind the Strengthscope approach!
