Effect of SEM differences on confidence intervals Flashcards
What does SEM measure?
SEM is a measure of how much test scores are spread around a “true” score
What is the APA definition of SEM?
“The standard deviation of errors of measurement that is associated with the test scores for a specified group of test takers” (APA, 1985)
What is the formula for SEM?
SEM=s√(1-r)
Where r = the reliability of the test
and s = the standard deviation of the test
What is SEM usually accompanied by?
A confidence interval (CI)
What is a confidence interval?
A range around the estimated “true” score
What is the measurement unit for SEM?
The measurement unit is the same as the original test scores
E.g., if you’re measuring in points, the SEM will be in points and if you’re measuring in % the SEM will be in %
What is the formula for the 95% CI?
score ± (1.96*SEM)
The magnitude of differences on the variables that comprise the SEM impact Cis as follows: At the highest level, the larger the overall value of the SEM, the X the range in your CI.
The larger the overall value of the SEM, the greater the range in your CI.
In the SEM formula, there are two variables which we can change to impact our CIs, these are S, and r.
What happens to the CIs if we increase S?
If we increase S then the range of the CIs increases in tandem
In the SEM formula, there are two variables which we can change to impact our CIs, these are S, and r.
What happens to the CIs if we decrease S?
If we decrease S then the range of the CIs decreases in tandem
In the SEM formula, there are two variables which we can change to impact our CIs, these are S, and r.
What happens to the CIs if we increase r?
If we increase r, then the range of the CIs decreases
In the SEM formula, there are two variables which we can change to impact our CIs, these are S, and r.
What happens to the CIs if we decrease r?
If we decrease r, then the range of the CIs increases
