Characteristics of Successful Assessment Measures. Reliable Valid Efficient - Time - Money - Resources Don’t result in complaints. Reliability. What Do We Mean by Reliability?. The extent to which a score from a test is consistent and free from errors of measurement.
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(2 x split-half correlation)
(1 + split-half correlation)
If we have a split-half correlation of .60, the corrected reliability would be:
(2 * .60) ÷ (1 + .60) = 1.2 ÷ 1.6 = .75
L = the number of time longer the new test will be
Suppose you have a test with 20 items and it has a reliability of .50. You wonder if using a 60-item test would result in acceptable reliability.
Estimated New Reliability = .75
The degree to which inferences from scores on tests or assessments are justified by the evidence
Validity refers to the degree to which evidence and theory support the interpretations of test scores entailed by proposed uses of tests. ... The process of validation involves accumulating evidence to provide a sound scientific basis for the proposed score interpretations. It is the interpretations of test scores required by proposed uses that are evaluated, not the test itself. When test scores are used or interpreted in more than one way, each intended interpretation must be validated. Sources of validity evidence include but not limited to: evidence based on test content, evidence based on response processes, evidence based on internal structure, evidence based on relations to other variables, evidence based on consequences of testing.
Standards for Educational and Psychological Testing (1999)
What is the content of this exam?
Known Group Validity