In other words, does it “look like” it will measure what it should do. For example, a questionnaire aiming to score anxiety should include questions aimed at a broad range of features of anxiety.Face validity is the degree to which a test is subjectively thought to measure what it intends to measure. Construct validity subsumes the other types of validity.Content validity describes whether an instrument is systematically and comprehensively representative of the trait it is measuring. For example, a measure of intelligence should only assess factors relevant to intelligence and not, for instance, whether someone is a hard worker. Assessment for reliability and validity of measurement.Construct validity is the extent to which the instrument specifically measures what it is intended to measure, and avoids measuring other things. There are four main types of validity:that it is relevant to discuss the methods of analysis of instruments measurement properties in.
There are different means for testing the reliability of an instrument: Reliability is also known as reproducibility or repeatability. A highly reliable measure produces similar results under similar conditions so, all things being equal, repeated testing should produce similar results. This can take the form of concurrent validity (where the instrument results are correlated with those of an established, or gold standard, instrument), or predictive validity (where the instrument results are correlated with future outcomes, whether they be measured by the same instrument or a different one).Reliability is the overall consistency of a measure.
It is more robust than simple percentage agreement as it accounts for the possibility that a repeated measure agrees by chance. Kappa indicates how well two sets of (categorical) measurements compare. Cronbach’s alpha values above 0.7 are generally deemed acceptable.Inter-rater reliability can be measured using the Cohen’s kappa (k) statistic. Ranging from minus infinity to one, a Cronbach’s alpha of one indicates perfect internal consistency, and a negative value suggests that there is greater within-subject variability than there is between subjects. This is also known as equivalence.This is the degree of agreement, or consistency, between different parts of a single instrument.Internal consistency can be measured using Cronbach’s alpha (a) – a statistic derived from pairwise correlations between items that should produce similar results. Intra-rater (or intra-observer) reliabilityAlso known as test-retest reliability, this describes the agreement between results when the instrument is used by the same observer on two or more occasions (under the same conditions and in the same test population).This is the degree to which two or more instruments, that are used to measure the same thing, agree on the result.
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