Scales of Measurement & Desig Flashcards
Validity of a Test
Is the extent to which it measures what it claims to measure
Can a test be Reliable and Valid?
To the extent that a test is unreliable it cannot be valid
e.g. weighing on a scale that consistently adds 10 lbs…. it is reliable but not valid
A test is valid
To the extent that inferences made from it are appropriate, meaningful and useful.
Three categories of validity evidence
Content Validity
Criterion-Referenced Validity
Construct Validity
Content Validity
Is determined by the degree to which the questions, tasks, or items on a test are representative of the universe of behavior the test was designed to sample
If the sample (specific items on the steps) is representative of the population (all possible items), then the test possesses content validity
Face Validity
Is not really a form of validity at all
A test has Face Validity if it looks valid to test users, examiners and especially, the examiner.
Should not be confused with Objective Validity
Objective Validity
Is determined by the relationship of test scores to other sources of information
Criterion-Related Validity
Is demonstrated when a test is shown to be effective in estimating an examinee’s performance on some outcome measure. The variable of primary interest is the outcome measure, called a CRITERION.
Two different approaches to Validity evidence
Concurrent Validity
Predictive Validity
Concurrent Validity
Criterion measures are obtained at approximately the same time as the test scores
Predictive Validity
The criterion measures are obtained in the future (usually months/years after the test scores are obtained.
E.g., college entrance exams
Characteristics of a good Criterion
- Must itself be reliable if it is to be a useful index of what the test measures
- A criterion measure must also be appropriate for the test under investigation
- All criterion measures should be described accurately, and the rationale for choosing them as relevant criteria should be made explicit
- A criterion must also be free of contamination from the test itself
Criterion
Is any outcome measure against which a test is validated.
It can be most anything
Validity Coefficient
See pg 76
The validity coefficient is always less than or equal to the square root of the test reliability multiplied by the criterion reliability.
In other words, to the extent that the reliability of either the test of the criterion (or bothz0 is low, the validity coefficient is also diminished.
Criterion Contamination
Potential source of error in test validation
The criterion is “contaminated” by its artificial commonality with the test
Also possible when the criterion consists of ratings from experts.
Concurrent Validity
- Test scores and criterion information are obtained simultaneously.
- Usually desirable for achievement tests, tests used for licensing or certification, and diagnostic clinical tests.
- Indicated the extent to which test scores accurately estimate an individual’s present position on the relevant criterion.
Predictive Validity
- Test scores are used to estimate outcome measures obtained at a later date.
- Relevant for entrance exams and employment tests—common endeavor of thies tests:determining who is likely to succeed at a future endeavor.