MEASUREMENT CONCEPTS

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Define reliability of a measure of behavior and describe the difference between test-retest, internal consistency, and interrater reliability

Discuss ways to establish construct validity, including predictive validity, concurrent validity, convergent validity, and discriminant validity

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Describe the problem of reactivity of a measure of behavior and discuss ways to minimize reactivity

Describe the properties of the four scales of measurement: nominal, ordinal, interval, and ratio

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Consistency or Stability of a Measure of Behavior

True Score Measurement Error Pearson Product-Moment Correlation

Coefficient

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- 1.00 + 1.000.00

Variables covary in opposite directions

Variables covary in the same

direction

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Test-Retest Reliability Assessed by measuring the same individuals two points

in time Vulnerable to artificiality Vulnerable to maturation

Internal Consistency Reliability Split-half reliability Cronbach’s alpha

Correlation of each item on the measure all other items on the measure

Item-total correlations© 2012 The McGraw-Hill Companies, Inc.

Interrater Reliability Correlation between the observations of raters

Reliability and Accuracy of Measures Reliability indexes do not indicate whether a

particular measure is an accurate measure of the variable of interest

A measure can be highly reliable but not accurate

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Less error

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Indicators of Construct Validity Face validity Content validity

Predictive validity Concurrent validity Convergent validity Discriminant validity

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Face Validity The content of the measure appears to reflect the construct being measured

Content validity The content of the measure is linked to the universe of content that defines the construct

Predictive validity Scores on the measure predict behavior on a criterion measured at a time in the future

Concurrent validity Scores on the measure are related to a criterion measured at the same time (concurrently)

Convergent validity Scores on the measure are related to other measures of the same construct

Discriminant validity Scores on the measure are not related to other measures that are theoretically different

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Systematic and detailed research on validity is most often carried out on measures of personality and individual differences

Should use measures of personality that have demonstrable validity and reliability Example: Mental Measurement Yearbook

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Measure is reactive if awareness of being measured changes an individual’s behavior

Measures of behavior vary in terms of their potential reactivity

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Nominal Scales Ordinal Scales Interval and Ratio Scales The Importance of the Measurement Scales

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Scale Description Example Distinction

Nominal Categories with no numeric scales

Males / femalesIntroverts / extroverts

Impossible to define any quantitative values

Ordinal Rank orderingnumeric values limited

2-, 3-, and 4-star restaurantsRanking TV programs by popularity

Intervals between items is unknown

Interval Numeric properties are literalAssume equal intervals between values

IntelligenceAptitude test scoresTemperature (Fahrenheit and Celsius)

No true zero point

Ratio Zero indicates absence of variable measured

Reaction timeWeightAge Frequency of behavior

Can form ratios (someone weighs twice as much as another)