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Chapter 6

PSYC 3090 Chapter 6: CHAPTER 6

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PSYC 3090
Krista Trobst

CHAPTER 6 – VALIDITY -something is valid if it is sound, meaningful, or well grounded on principles or evidence Concept of Validity Validity: judgment or estimate of how well a test measures what it purports to measure in a particular context Inference: logical result or deduction -how useful instrument is for a particular purpose with a particular population of people -test is shown to be valid for particular use with a particular population of testtakers at a particular time -no test or measurement technique universally valid for all time, all uses and all types of testtaker populations -tests valid within what we characterize as reasonable boundaries of contemplated usage Validation: the process of gathering and evaluating evidence about validity Validation studies: research that entails gathering evidence relevant to how well a test measures what it purports to measure for the purpose of evaluating the validity of a test or other measurement tool Local validation studies: the process of gathering evidence, relevant to how well a test measures what it purports to measure, for the purpose of evaluating the validity of a test or other measurement tool; typically undertaken in conjunction with a population different from the population for whom the test was originally validated 3 categories of validity 1. Content validity – measure of validity based on an evaluation of the subjects, topics, or content covered by the items in the test 2. Criterion-related validity – measure of validity obtained by evaluating the relationship of scores obtained on the test to scores on other tests or measures 3. Construct validity – measure of validity that is arrived at by executing a comprehensive analysis of: a. How scores on the test relate to other test scores and measures and b. How scores on the test can be understood within some theoretical framework for understanding the construct that the test was designed to measure -classic conception of validity referred to as Trinitarian view -not mutually exclusive Face Validity Face validity: what a test appears to measure to the person being tested than to what the test actually measures -lack of face validity may contribute to lack of testtaker cooperation -parents may object to having their children tested that seem invalid -in reality, face validity does not relate to actually test relevance Content Validity Content validity: a judgment regarding how adequately a test samples behaviour representative of the universe of behaviour it was designed to sample -must have key components of the construct targeted for measurement and exclude content irrelevant to the constructed targeted for measurement Test blueprint: a detailed plan of the content, organization and quantity of the items that a test will contain The Quantification of content validity -lawshe: for each item, each rater needs to answer is item essential, useful but not essential and not necessary -if more than half indicate its essential, that item has some content validity -developed formula Content validity ratio (CVR): used to gauge agreement among raters regarding how essential an individual test item is for inclusion in a test -negative = less than half, 0 = exactly half, and positive = more than half -if amount of agreement observed more than 5% likely to occur by chance, the item should be eliminated Culture and the relativity of content validity -history tests, politics (what is considered true and not true) Criterion-Related Validity Criterion-related validity: judgement of how adequately a test score can be used to infer an individual’s most probable standing on some measure of interest Concurrent validity: index of the degree to which a test score is related to some criterion measure obtained at the same time Predictive validity: index of the degree to which a test score predicts some criterion measure What is a Criterion? Criterion: the standard against which a test or test score is evaluated, this standard may take many forms, including a specific behaviour or set of behaviours Characteristics of a criterion -adequate criterion is relevant -criterion must be valid -criterion must be uncontaminated Criterion contamination: a state in which a criterion measure is itself based, in whole or in part, on a predictor measure -example on page 191 -no methods or statistics to gauge extent to which criterion contamination has taken place, or to correct it Concurrent Validity -if test scores obtained at about the same time as the criterion measures are obtained, measures of the relationship between the test scores and the criterion provide evidence of concurrent validity Predictive Validity -test scores may be obtained at one time and the criterion measures obtained at a future time -how accurately scores on the test predict some criterion measure -judgements of criterion-related validity based on 2 types of statistical evidence: validity coefficient and expectancy data Validity Coefficient Validity coefficient: correlation coefficient that provides a measure of the relationship between test scores and scores on the criterion measure -typically, pearson correlation used -others can be used -affected by restriction or inflation of range -key issue is whether range of scores employed is appropriate to the objective of the correlational analysis -no rules for determining minimum acceptable size of a validity coefficient Incremental Validity -often interested in utility of multiple predictors -value of including more than one predictor depends on couple of factors 1. Each measure used as a predictor should have criterion-related predictive validity 2. Additional predictors should have incremental validity a. Incremental validity: the degree to which an additional predictor explains something about the criterion measure that is not explained by predictors already in use Expectancy data Expectancy data: information, usually in the form of an expectancy table, illustrating the likelihood that an individual testtaker will score within some interval of scores on a criterion measure Expectancy table: shows the percentage of people within specified test-score intervals who subsequently were placed in various categories of the criterion Expectancy chart: graphic representation of an expectancy table Construct Validity Construct validity: judgment about the appropriateness of inferences drawn from test scores regarding individual standings on a variable called a construct Construct: informed, scientific idea developed or hypothesized to describe or explain behaviour -unobservable, presupposed traits that a test developer may invoke to describe test behaviour or criterion performance -must formulate hypotheses about expected behaviour of high scorers + lo
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