Product Reliability Measuring WWW.KAASHIVINFOTECH.COM

LEARNING OBJECTIVES 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 WWW.KAASHIVINFOTECH.COM

LEARNING OBJECTIVES 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 WWW.KAASHIVINFOTECH.COM

RELIABILITY OF MEASURES Consistency or Stability of a Measure of Behavior True Score Measurement Error Pearson Product-Moment Correlation Coefficient WWW.KAASHIVINFOTECH.COM

Pearson’s product moment correlation coefficient (r) - 1.00 + 1.00 0.00 Variables covary in opposite directions Variables covary in the same direction WWW.KAASHIVINFOTECH.COM

RELIABILITY OF MEASURES 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 WWW.KAASHIVINFOTECH.COM

RELIABILITY OF MEASURES 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 WWW.KAASHIVINFOTECH.COM

Less error WWW.KAASHIVINFOTECH.COM

CONSTRUCT VALIDITY OF MEASURES Indicators of Construct Validity Face validity Content validity Predictive validity Concurrent validity Convergent validity Discriminant validity WWW.KAASHIVINFOTECH.COM

Construct Validity 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 WWW.KAASHIVINFOTECH.COM

RESEARCH ON PERSONALITY AND INDIVIDUAL DIFFERENCES 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 WWW.KAASHIVINFOTECH.COM

REACTIVITY OF MEASURES Measure is reactive if awareness of being measured changes an individual’s behavior Measures of behavior vary in terms of their potential reactivity WWW.KAASHIVINFOTECH.COM

VARIABLES AND MEASUREMENT SCALES Nominal Scales Ordinal Scales Interval and Ratio Scales The Importance of the Measurement Scales WWW.KAASHIVINFOTECH.COM

Scales of measurement Scale Description Example Distinction Nominal Categories with no numeric scales Males / females Introverts / extroverts Impossible to define any quantitative values Ordinal Rank ordering numeric values limited 2-, 3-, and 4-star restaurants Ranking TV programs by popularity Intervals between items is unknown Interval Numeric properties are literal Assume equal intervals between values Intelligence Aptitude test scores Temperature (Fahrenheit and Celsius) No true zero point Ratio Zero indicates absence of variable measured Reaction time Weight Age Frequency of behavior Can form ratios (someone weighs twice as much as another) WWW.KAASHIVINFOTECH.COM

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