1. Product Reliability Measuring

2. 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

3. 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

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

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

6. 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

7. 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

8. Less error

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

10. 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

11. 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

12. 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

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

14. 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)

15. Thank You
© 2007 The McGraw-Hill Companies, Inc.