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Validity refers to the degree to which a test accurately measures what it is designed to measure. Tests of intelligence should measure intelligence, tests of depression should measure depression, and so forth (Hogan & Tsushima, 2018).

Whereas reliability reflects consistency, validity refers to accuracy. Imagine a poor archer whose arrows are scattered across a target in a random pattern. The poor archer shows low reliability (as evidenced by his scattered arrows) and low validity (because he missed the bullseye). Now imagine a better archer whose five arrows are clustered together but distant from the bullseye. The better archer displays high reliability (as evidenced by his consistent pattern) but low validity (because he also missed the bullseye). Finally, imagine Katniss Everdeen, whose arrows are clustered together within the bullseye. Katniss shows high reliability and validity, like an ideal psychological test (Figure 4.5).

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Figure 4.5 ■ Reliability and Validity

Note: Reliability refers to the consistency of test scores; validity refers to their accuracy. Psychological tests must yield consistent scores that accurately measure the construct they are designed to measure.

Technically speaking, validity is not a property of a test itself. Instead, validity refers to the degree to which the test can be accurately used to serve a specific purpose (Hogan & Tsushima, 2018). Imagine that you record your daily physical activity with your Fitbit for 1 month. Your daily activity level is very high (10,000 steps) and relatively consistent (i.e., reliable) each day. Consequently, you might conclude that you are in excellent health. However, when you visit your doctor, she tells you that you have high blood pressure and cholesterol. The Fitbit may be a reliable measure of activity, but it may not be a valid measure of overall health. Similarly, a child’s WISC–V visual-spatial reasoning score may provide an accurate estimate of her visual-spatial reasoning, but it is probably not an accurate indicator of her reading or writing skills.

The validity of psychological tests can be examined in at least three ways. First, psychologists can look at the content validity of the test. Specifically, the content of test items should be relevant to the test’s purpose. For example, the Children’s Depression Inventory, Second Edition (CDI-2; Kovacs, 2011) is the most widely used instrument to assess depression in children. The test includes items that reflect many of the diagnostic criteria for depression: “I am sad all the time,” “I am cranky all the time,” and “I have trouble sleeping every night.” The CDI-2 has excellent content validity because these items are consistent with the DSM-5 symptoms of depression.

Psychologists also examine the construct validity of the test (Cronbach & Meehl, 1955). Construct validity refers to the degree to which test scores reflect hypothesized attributes, or constructs. Most psychological variables are constructs: intelligence, depression, anxiety, aggression. Constructs cannot be measured directly; instead, they must be inferred from overt actions or people’s self-reports. For example, intelligence might be inferred from excellent grades in school, depression might be inferred from frequent crying, and aggression might be inferred from a history of physical fighting.

To investigate the construct validity of a test, psychologists examine the relationship of test scores to other measures of similar and dissimilar constructs. Evidence of convergent validity comes from significant relationships between test scores and theoretically similar constructs. Evidence of discriminant validity comes from nonsignificant relationships between test scores and theoretically dissimilar constructs. For example, the convergent validity of the CDI-2 is supported by high correlations with other measures of childhood depression, whereas the discriminant validity of the CDI-2 is supported by lower correlations with measures of other childhood problems such as anxiety and aggression.

Finally, psychologists examine the test’s criterion-related validity. Criterion-related validity refers to the degree to which test scores can be used to infer a probable standing on some external benchmark, or criterion. One measure of criterion-related validity is called concurrent validity, the degree to which test scores are related to some criterion at the same point in time. For example, children with depression should score significantly higher on the CDI-2 than children without depression. Another aspect of criterion-related validity is called predictive validity. Predictive validity refers to the ability of test scores to predict theoretically expected outcomes. For example, children who earn high CDI-2 scores may be at risk for suicidal thoughts and actions in the future (Geisinger, 2018).

Review

 Standardized tests are administered, scored, and interpreted in the same way to all children. Most standardized tests are norm-referenced. They yield scores that quantify the degree to which the child’s performance is similar to that of his or her peers.

 Reliability refers to a test’s consistency. Examples include test–retest reliability, inter-rater reliability, and internal consistency.

 Validity refers to a test’s ability to accurately reflect a desired construct. Examples include content validity, construct validity, and criterion-related validity.