Validity

Validity is a concept that is central to understanding the reliability and trustworthiness of measurements and observations. It refers to the extent to which a test measures what it claims to measure. Validity is important in both qualitative and quantitative research.

Types of Validity

There are several types of validity, including:

• Content Validity: This refers to the extent to which a measure represents all facets of a given construct. For example, a depression scale may lack content validity if it only assesses the affective dimension of depression but fails to take into account the behavioral dimension.

• Criterion Validity: This is the extent to which a measure is related to an outcome. Criterion validity is often divided into concurrent and predictive validity.

• Construct Validity: This is the degree to which a test measures what it claims, or purports, to be measuring.

• Face Validity: This is the extent to which a test is subjectively viewed as covering the concept it purports to measure.

Threats to Validity

There are several threats to validity, including:

• History: This refers to the specific events occurring between the first and second measurements in addition to the experimental variables.

• Maturation: This refers to processes within the participants as a function of the passage of time.

• Testing: This refers to the effects of taking a test upon the scores of a second testing.

• Instrumentation: This refers to changes in calibration of a measurement tool or changes in the observers or scorers may produce changes in the obtained measurements.

See Also

• Reliability (statistics)
• Measurement Theory
• Psychometrics

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