Test Validity and Reliability

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1. Can you explain in easy to understand language the different types of test validity and reliability? Thank you.

Test Validity and Reliability

Whenever a test or other measuring device is used as part of the data collection process, the validity and reliability of that test is important. Just as we would not use a math test to assess verbal skills, we would not want to use a measuring device for research that was not truly measuring what we purport it to measure. After all, we are relying on the results to show support or a lack of support for our theory and if the data collection methods are erroneous, the data we analyze will also be erroneous.

Test Validity. Validity refers to the degree in which our test or other measuring device is truly measuring what we intended it to measure. The test question "1 + 1 = _____" is certainly a valid basic addition question because it is truly measuring a student's ability to perform basic addition. It becomes less valid as a measurement of advanced addition because as it addresses some required knowledge for addition, it does not represent all of knowledge required for an advanced understanding of addition. On a test designed to measure knowledge of American History, this question becomes completely invalid. The ability to add two single digits has nothing do with history.

For many constructs, or variables that are artificial or difficult to measure, the concept of validity becomes more complex. Most of us agree that "1 + 1 = _____" would represent basic addition, but does this question also represent the construct of intelligence? Other constructs include motivation, depression, anger, and practically any human emotion or trait. If we have a difficult time defining the construct, we are going to have an even more difficult time measuring it. Construct validity is the term given to a test that measures a construct accurately and there are different types of construct validity that we ...