1. Reliability and validity

2. Reliability vs. validity
Consistency
True score + measurement error
Validity
Truth
Can a scale be reliable but not valid?
Can a scale be valid but not reliable?

3. Types of reliability Test-retest Alternate forms Internal consistency
Split-half
Odd-even
Cronbach’s alpha (item-total reliability)
Inter-rater reliability

4. Types of validity Face validity Construct validity
Convergent
Divergent/discriminant
Known groups
Criterion-related validity
Concurrent
Predictive

5. Problems for validity
Demand characteristics
Social desirability

6. Other types of validity
Internal validity
External validity

7. Types of scaling Nominal (difference) Ordinal (magnitude)
Interval (equal intervals)
Ratio (true zero)

8. Why do scale types matter?
More properties, more information
Affect the statistics you can do
Helps you evaluate research

9. What types of scales are these?
1. October 22, 1850 (year Fechner’s law)
2. number of alarm class by a chickadee in one hour
3. third place in a beauty contest
4. having the fifth highest grades in a class of 29 people
5. being a sophomore in college
6. Thurstone scale
7. Guttman scale
8. Likert scale
9. Semantic differential