Methods of validating a test instrument

(the process of developing, testing, and using the device).

It is rare, if nearly impossible, that an instrument be 100% valid, so validity is generally measured in degrees.As a process, validation involves collecting and analyzing data to assess the accuracy of an instrument.There are numerous statistical tests and measures to assess the validity of quantitative instruments, which generally involves pilot testing.The remainder of this discussion focuses on external validity and content validity. Establishing eternal validity for an instrument, then, follows directly from sampling.Recall that a sample should be an accurate representation of a population, because the total population may not be available.

An instrument that is externally valid helps obtain population generalizability, or the degree to which a sample represents the population.

refers to the appropriateness of the content of an instrument.

In other words, do the measures (questions, observation logs, etc.) accurately assess what you want to know?

This is particularly important with achievement tests.

Consider that a test developer wants to maximize the validity of a unit test for 7th grade mathematics.

This would involve taking representative questions from each of the sections of the unit and evaluating them against the desired outcomes. Does the instrument consistently measure what it is intended to measure?