A conceptual introduction to psychometrics by G, J., Mellenbergh - a summary

This is a summary of the book A conceptual introduction to psychometrics by G, J., Mellenbergh. The summary contains chapter 1 to 6, and focusus on developing psychological tests.

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Introduction - a summary of chapter 1 of A conceptual introduction to psychometrics by G, J., Mellenbergh

A conceptual introduction to psychometricsChapter 1Introduction Psychometric terminology sometimes differs depending on the types of test applications.A psychological or educational test: an instrument for the measurement of a person’s maximum or typical performance under standardized conditions, where the performance is assumed to reflect one or more latent attributes.A test is defined to be a measurement instrument. It is for measurement in the first place.A test is defined to measure performance. Two types of performance:Maximum performance tests ask the person to do his or her best to solve one or more problems. The answers to this problems can vary in correctness.Typical performance tests asks the person to respond to one or more tasks where the responses are typical for the person. The person’s responses cannot be evaluated on correctness, but they typify the person.Performance is measured under standardized conditions.Test performance must reflect one or more latent attributes. The test performance is observable, but the latent attributes cannot be observed.Tests are distinguished form surveys. It is not assumed that survey questions reflect a latent attribute.Subtest: an independent part of a test.A (sub)test consists of one or more items.Item: the smallest possible subtest of a test. The building blocks of a test.A test consists of n items, and is called a n-item test.One or more latent attributes effect test performance.The number of latent attributes is the dimensionality of the test.Dimensionality: equal to the number of latent attributes (variables), which effects test performance.Unidimensional test: a test that predominantly measures one...

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Developing maximum performance tests - a summary of chapter 2 of A conceptual introduction to psychometrics by G, J., Mellenbergh

A conceptual introduction to psychometricsChapter 2Developing maximum performance testsSeven elementsConstructMeasurement modeObjectivesPopulation and subpopulationsConceptual frameworkRespons modeAdministration mode The test developer must specify the latent variable of interest that has to be measured by the test.Latent variable is a general term. The term construct is used when a subsantive interpretation is given of the latent variable.The latent variable (construct) is assumed to effect test makers’ item responses and test scores.Constructs can vary in many different ways.Vary in content of mental abilities, psychomotor skills or physical abilitiesConstruct may vary in scopeFor example: from general intelligence to multiplication skillConstructs vary from educational to psychological variables.A good way to start a test development project is to define the construct that has to be measured by the test.This definition describes the construct of interest, and distinguished it from other, related, constructs.Usually, the literature on the construct needs to be studies before the definition can be given. Frequently the definition can only be given when other elements of the test development plan are specified. Different modes can be used to measure constructs.Self-performance modeThe test taker is is asked to...

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Typical performance tests - a summary of chapter 3 of A conceptual introduction to psychometrics by G, J., Mellenbergh

A conceptual introduction to psychometricsChapter 3Typical performance testsTypical performance tests assess behavior that is typical for the person.These tests are used to measure attitudes, interests, values, opinions, and personality characteristics. The test developer has to specify the latent variable of interest that is assumed to effect test takers’ item responses and test scores.The ususal constructs of interest of typical performance tests are:AttitudesInterestsValuesOpinionsPersonality characteristicsThe responses to typical performance tests are not evaluated on their correctness, but are considered to typify a person.At the start of a test development project, the researcher needs information on the construct of interest. This information can be obtained from different sourcesA study of the literature on the construct and existing measurement instruments is nearly always needed at the start of a test development projectDifferent types of research can be done on the construct.Focus group methodUses small groups of persons who have experiential knowledge about the construct.A focus group meets with the test developer to talk about their experiences with the construct.Key information methodUses persons who have expert knowledge about the construct of interest. The test developer interviews these key informants about the constructs.Observation methodThe test developer can use information from different sources...

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Observed test scores - a summary of chapter 4 of A conceptual introduction to psychometrics by G, J., Mellenbergh

A conceptual introduction to psychometricsChapter 4Observed test scoresThe aim of testing is to yield scores of test takers’ maximum or typical performance.Two main types of test scores are distinguishedObserved testComputed after the separate test items are scored.Derived from the item scores by taking the unweighted or weighted sum of the item scores.The latent variable is unobserved, and in general, the laten variable is not a simple sum of item scores.Latent variable (construct) scoresTo compute the latent variable score, a model is needed that specifies the relation between the latent variable and item responses.The latent variable score is derived from the item responses under the assumption of a latent variable item response model. Conventionally, items are scored by assigning ordinal numbers to the responses.The scoring differs slightly between maximum and typical performance tests.Maximum performance items are scored by assigning 0 to the lowest category, and consecutive rank numbers to subsequent categories.Typical performance items are indicative or contra-indicative of the latent variable that is measured by the test, and the scoring of contra-indicative item has to be reversed with respect to the scoring of indicative items.Dichotomous indicative typical performance items are scored assigning 0 to the ‘no’ (don’t agree), and 1 to the yes (agree) categorie.Whereas contra-indicative items are scored by assigning 0 to the ‘yes’, and 1 to the ‘no’ category.The categories of ordinal-polytomous items are scored by assigning rank numbers to the categories.Bounded-continuous items ares cored in measurement...

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Classical analysis of observed test scores - a summary of chapter 5 of A conceptual introduction to psychometrics by G, J., Mellenbergh

A conceptual introduction to psychometricsChapter 5Classical analysis of observed test scores Test scores are used in practical applications.Measurement precision has two different aspects:InformationApplies to the test score of a single personThe within-person aspect of measurement precisionReliabilityApplies to a population of persons.The between-persons aspect of measurement precisionThe concept of measurement precision applies to observed test scores as well as to latent variable scores. Functional thought experiment: fulfils a function within a theory.True test score: the expected value of the observed test scores of the repeated test administrations in the thought experiment.Test taker j’s true test score is the expected value of his (or her) independently distributed observed tst scores from (hypothetical) repeated administrations of the test to the test taker.The observed test score is a variable that varies across repeated test administrations.The true score is constant.Error of measurement: the difference between test taker j’s observed test score and his (or her) true score.Test taker j’s error of measurement on an arbitrary measurement occasion is ht difference between his (or her) observed test score and his (or her) true test score.The expected value of the errors of measurement is 0.The within-person error variance is...

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Classical analysis of item scores - a summary of chapter 6 of A conceptual introduction to psychometrics by G, J., Mellenbergh

A conceptual introduction to psychometricsChapter 6Classical analysis of item scoresThe conventional way of scoring items is by assigning ordinal numbers to the response categories.Usually, these item scores are ordered with respect to the attribute that the item is assumed to measure. But, these assignment of these ordinal numbers lacks a theoretical justification.Usually, the analysis of test scores is supplemented by an analysis of the item scores. The scores of a given item have a distribution in a population of N persons.Location: the place of the scale where item scores are centeredDispersion: the scatter of the item scoresShape: the form of the distributionsClassical item difficulty and attractiveness The location of the item score distribution is used to define the classical item difficulty (maximum performance tests) and classical item attractiveness (typical performance tests) concepts.Classical item difficulty: a parameter that indicates the location of the item score distribution in a population of persons.Classical item attractiveness: a parameter that indicates the location of the item score distribution in a population of persons.The two definitions are the same.Classical item difficulty and attractiveness are defined in a population of persons.Population-dependent and may differ between populations.The mean in mainly used for this.The mean of a dichotomously scored item is called the item p-value.Item score variance and standard deviation The most common parameters that are used in classical item score analysis are the variance and the standard...

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