|The formula for r looks like this:|
|nominal||ordinal||Rank biserial coefficient (rrb)|
|nominal||interval/ratio||Point biserial coefficient (rpb)|
|ordinal||ordinal||Spearman rank-order coefficient (rho)|
|Type of Reliability||Application|
|Test-retest||Use this type of reliability estimate
whenever you are measuring a trait over a period of time.
Example: teacher job satisfaction during the school year
|Parallel forms||Use this type of reliability estimate
whenever you need different forms of the same test to measure the same
Example: multiple forms of the SAT
|Internal consistency||Use this type of reliability estimate
whenever you need to summarize scores on individual items by an overall
Example: combining the 20 items on a statistics test to represent level of knowledge about a particular aspect of statistics
|Interrater||Use this type of reliability estimate
whenever you involve multiple raters in scoring tests.
Example: AP essay test grading
|Type of Validity||Application|
|Content||Use this type of validity estimate
whenever you are comparing test items with a larger domain of knowledge.
Example: assessing the breadth of a comprehensive final exam
|Criterion||Use this type of validity estimate
whenever you are comparing a new test with an established standard.
Example: developing a test to predict genius (predictive), or developing a new test comparable to the CAHSEE (high school exit exam)
|Construct||Use this type of validity estimate
whenever you are comparing a test with the elements of a theoretical
definition of a trait.
Example: developing a new test for musical intelligence - distinguishing between musical and other types of intelligence