1. Measurement of Variables What are the Four Types of Psychological Measures? What are the Four Types of Psychological Measures? What are the Four Types of Psychological Measures? What are the Four Types of Psychological Measures? What are the Four Measurement Scales? What are the Four Measurement Scales? What are the Four Measurement Scales? What are the Four Measurement Scales? What are Discrete and Continuous Variables? What are Discrete and Continuous Variables? What are Discrete and Continuous Variables? What are Discrete and Continuous Variables?

2. Types of Measures Self-Report Self-Report Tests Tests Behavioral Measures Behavioral Measures Physical Measures Physical Measures

3. Measurement Scales The measurement scale tells you what assumptions you can make about a score. The measurement scale tells you what assumptions you can make about a score. Many statistics require a certain measurement scale. Many statistics require a certain measurement scale. The measurement scale is a property of the data, not a decision made by the researcher. The measurement scale is a property of the data, not a decision made by the researcher.

4. Nominal Scale Numbers classify into groups. Numbers classify into groups. Math, other than counting, is not meaningful. Math, other than counting, is not meaningful. EXAMPLES: EXAMPLES: gender gender hair color hair color

5. Ordinal Scale Numbers are rank orders. Numbers are rank orders. Most mathematical operations are not meaningful. Most mathematical operations are not meaningful. EXAMPLES: EXAMPLES: order of finish in a race order of finish in a race class rank class rank

6. Interval Scale Numbers represent amounts, with equal intervals between numbers. Numbers represent amounts, with equal intervals between numbers. Math, other than ratio comparisons, is meaningful. Math, other than ratio comparisons, is meaningful. EXAMPLES: EXAMPLES: score on intelligence test score on intelligence test temperature in Celsius temperature in Celsius

7. Ratio Scale Numbers represent amounts, with equal intervals and an absolute zero Numbers represent amounts, with equal intervals and an absolute zero absolute zero: zero represents complete absence absolute zero: zero represents complete absence Math, including ratios, is meaningful. Math, including ratios, is meaningful. EXAMPLES: EXAMPLES: number of seconds to finish number of seconds to finish temperature in Kelvin temperature in Kelvin

8. Why You Can’t do Ratios on an Interval Scale

9. The Same Temperatures on Another Interval Scale

10. The Same Temperatures with Absolute Zero Shown

11. The Same Temperatures on a Ratio Scale (Rankine = F + 459.6)

12. The Same Temperatures on a Ratio Scale (Kelvin = C + 273.15)

13. Discrete vs. Continuous Variables discrete: separate, whole number values discrete: separate, whole number values EXAMPLE: number of pets EXAMPLE: number of pets continuous: continuum including fractional values continuous: continuum including fractional values EXAMPLE: height EXAMPLE: height

14. Real Limits A score on a continuous variable is really an interval. A score on a continuous variable is really an interval. The real limits are half a unit down and half a unit up from the measured score. The real limits are half a unit down and half a unit up from the measured score. measured score = 65 inches measured score = 65 inches real limits: 64.5-65.5 inches real limits: 64.5-65.5 inches