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Assessment Instrument Glossary


In the clinical context, the primary goal of assessment is to determine those characteristics of the client and his or her life situation that may influence treatment decisions and contribute to the success of treatment. Additionally, assessment procedures are crucial to the treatment planning process, which involves the integration of assessment information concerning the person's substance use behavior, substance-related problems, and other areas of psychological and social functioning. Assessment instruments may also be geared towards assessing the treatment and treatment process itself, or in assessment of treatment outcomes.


Norms allow the test performance of a given client to be compared with that of a large, relevant group of individuals. No instrument is validly useful for all people. While norms are essential to describe a single case of a sample by comparison to a larger group, they are less important, for example, in contrasting pretreatment and post-treatment behavior in an individual. In determining the importance of normative information, the clinician should be concerned about whether norms are available that would assist in making clinical decisions in a particular case. Phrased differently, would the demographic characteristics of a client affect the interpretation of the score and influence choice of treatment?


Reliability: A measure is considered reliable if it would give the same result over and over again. Reliability is measured several ways:

  • Inter-rater (or joint): A measure of agreement between two or more observers evaluating the same subjects and using the same information. Used to assess the degree to which different raters give consistent estimates of the same phenomenon.

  • Test-retest (or stability): A measure of agreement between evaluations at two points in time. One would expect high stability on measures that tap stable client characteristics, such as family history of alcoholism, age of onset of problem drinking, and general expectancies of alcohol effects. Scales for more transient client characteristics, such as craving and treatment motivation, would be expected to have lower test-retest reliability.

  • Internal (or internal consistency): Reflects agreement of content coverage within the scale itself. Internal consistency assess how well responses on individual items correlate with those of other items of the scale. Internal consistency is often assessed by correlating performance on two halves of a test ("split-test"). For instruments designed to measure a single phenomenon, such as severity of the alcohol dependence syndrome, these correlational coefficients should be high.

Validity: Refers to the degree to which a test measures what it is intended to measure. A test is valid for a particular purpose or for a particular group. Validity is measured in three ways:

  • Construct: Refers to the degree to which a measure actually taps a meaningful hypothetical construct and a nondirectly observable, underlying causal or explanatory dimension of behavior. Scales measuring hypothetical constructs such as "craving," "loss of control," and "denial," should yield high levels of construct validity.

  • Content: Refers to the degree to which the content of a measurement is related to the phenomenon or trait that it purports to measure. For example, a checklist of alcohol consequences should comprise the multiplicity of adverse effects of drinking, rather than singling out certain negative consequences to the minimization or exclusion of others that are equally damaging. Content validity is not quantified. Rather, it must be built into the test by careful construction and selection of test items, and is based on the content of a single measurement instrument.

  • Criterion: Refers to how well scores on a measure relate to important, relevant nontest (real world) behaviors, such as initial motivation for treatment and long-term maintenance of sobriety. Criterion validity is a major concern in evaluating screening tests and is gauged by the extent to which individuals who score positive on them actually receive a diagnosis of alcoholism and vice versa. Predictive, concurrent, and "postdictive" validity are all types of criterion validity. The distinctions among them reflect the temporal relationship between the test results and the phenomenon of interest.

  • Discriminate (convergent or divergent): The extent to which an instrument is effective in distinguishing between two or more groups of individuals with respect to specific traits or characteristics. For example, a test of drug abuse that has discriminate validity would make it possible to classify some individuals as definite drug abusers, others as mild drug users (who use drugs only occasionally) and still others who are almost totally free of drug use.

  • Face: The items of the test deal with information, questions, or problems related to the stated objectives of the test.


Screening refers to the formal process of testing to identify individuals with substance-related problems or consequences, or those who are at risk for such difficulties. Screening is used to determine whether a client does or does not warrant further assessment at the current time. It typically involves answering a "yes" or "no" question: Does the client being screened show signs of a possible mental health, substance-related, or co-occurring disorder? Note that the screening process does not necessarily identify what diagnosis the person may have, or how serious it might be, just whether or not further assessment is warranted.

Test Accuracy

Negative Predictive Value: The propotion of people who screen negative that actually do not have the disease.

Positive Predictive Value: The proportion of people who screen positive that actually have the disease.

Sensitivity: The proportion of diseased people who are correctly identified as "positive" by the measure.

Specificity: The proportion of non-diseased people who are correctly identified as "negative" by the measure.

SOURCES: Assessing Alcohol Problems: A Guide for Clinicians and Researchers, 2nd ed. Edited by: John P. Allen, Veronica B. Wilson. (NIH Publication No. 03-3745). Bethesda, MD: National Institute on Alcohol Abuse and Alcoholism, 2003. Available on-line at:
. Assessing Drug Abuse among Adolescents and Adults: Standardized Instruments: NIDA Clinical Report Series. Alfred S. Friedman and Samuel Granick. (NIH Publication No. 94-3757), Rockville: National Institute on Drug Abuse, 1994.

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