RELIABILITY & VALIDITY What is Reliability? How Can We Measure Reliability? What is Validity? What are the Types of Validity?

What is Reliability? Extent to which a measurement is consistent There is always measurement error when measuring variables. Larger measurement error means lower reliability.

Ways of Measuring Reliability Inter-rater Reliability Test-Retest Reliability Alternate Forms Reliability Split-Half Reliability

What is Validity? Extent to which a method measures what it is claimed to measure Reliability is a prerequisite for validity

Content Validity Extent to which an instrument includes appropriate content Consult experts about content of test

Construct Validity Extent to which the appropriate construct is measured Look for agreement with accepted measures of the same construct Review literature to determine appropriate variables that represent the construct

Criterion Validity Extent to which behaviors are accurately predicted Concurrent validity – present performance Predictive validity – future performance Use correlational research to determine and improve ability to predict

External Validity Extent to which the results can be generalized Improve ecological validity – how well the method represents appropriate situations/settings

Internal Validity Extent to which the results represent the relationship of interest Eliminate or control confounding variables - extraneous variables that change systematically with a variable of interest