MEASUREMENT CONCEPTS © 2012 The McGraw-Hill Companies, Inc.

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 © 2012 The McGraw-Hill Companies, Inc.

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 © 2012 The McGraw-Hill Companies, Inc.

Consistency or Stability of a Measure of Behavior True Score Measurement Error Pearson Product-Moment Correlation Coefficient © 2012 The McGraw-Hill Companies, Inc.

Variables covary in opposite directions Variables covary in the same direction © 2012 The McGraw-Hill Companies, Inc.

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 © 2012 The McGraw-Hill Companies, Inc.

Less error © 2012 The McGraw-Hill Companies, Inc.

Indicators of Construct Validity Face validity Content validity Predictive validity Concurrent validity Convergent validity Discriminant validity © 2012 The McGraw-Hill Companies, Inc.

Face ValidityThe content of the measure appears to reflect the construct being measured Content validityThe content of the measure is linked to the universe of content that defines the construct Predictive validityScores on the measure predict behavior on a criterion measured at a time in the future Concurrent validityScores on the measure are related to a criterion measured at the same time (concurrently) Convergent validityScores on the measure are related to other measures of the same construct Discriminant validityScores on the measure are not related to other measures that are theoretically different © 2012 The McGraw-Hill Companies, Inc.

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 © 2012 The McGraw-Hill Companies, Inc.

Measure is reactive if awareness of being measured changes an individual’s behavior Measures of behavior vary in terms of their potential reactivity © 2012 The McGraw-Hill Companies, Inc.

Nominal Scales Ordinal Scales Interval and Ratio Scales The Importance of the Measurement Scales © 2012 The McGraw-Hill Companies, Inc.

ScaleDescriptionExampleDistinction NominalCategories with no numeric scales Males / females Introverts / extroverts Impossible to define any quantitative values OrdinalRank ordering numeric values limited 2-, 3-, and 4-star restaurants Ranking TV programs by popularity Intervals between items is unknown IntervalNumeric properties are literal Assume equal intervals between values Intelligence Aptitude test scores Temperature (Fahrenheit and Celsius) No true zero point RatioZero indicates absence of variable measured Reaction time Weight Age Frequency of behavior Can form ratios (someone weighs twice as much as another)