Measurement of variables
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Measurement of Variables. What are the Four Types of Psychological Measures? What are the Four Measurement Scales? What are Discrete and Continuous Variables?. Types of Measures. Self-Report Tests Behavioral Measures Physical Measures. Measurement Scales.

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Measurement of Variables

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Measurement of variables

Measurement of Variables

  • What are the Four Types of Psychological Measures?

  • What are the Four Measurement Scales?

  • What are Discrete and Continuous Variables?


Types of measures

Types of Measures

  • Self-Report

  • Tests

  • Behavioral Measures

  • Physical Measures


Measurement scales

Measurement Scales

  • The measurement scale tells you what assumptions you can make about a score.

  • Many statistics require a certain measurement scale.

  • The measurement scale is a property of the data, not a decision made by the researcher.


Nominal scale

Nominal Scale

  • Numbers classify into groups.

  • Math, other than counting, is not meaningful.

  • EXAMPLES:

    • gender

    • hair color


Ordinal scale

Ordinal Scale

  • Numbers are rank orders.

  • Most mathematical operations are not meaningful.

  • EXAMPLES:

    • order of finish in a race

    • class rank


Interval scale

Interval Scale

  • Numbers represent amounts, with equal intervals between numbers.

  • Math, other than ratio comparisons, is meaningful.

  • EXAMPLES:

    • score on intelligence test

    • temperature in Celsius


Ratio scale

Ratio Scale

  • Numbers represent amounts, with equal intervals and an absolute zero

  • absolute zero: zero represents complete absence

  • Math, including ratios, is meaningful.

  • EXAMPLES:

    • number of seconds to finish

    • temperature in Kelvin


Why you can t do ratios on an interval scale

Why You Can’t do Ratios on an Interval Scale


The same temperatures on another interval scale

The Same Temperatures on Another Interval Scale


The same temperatures with absolute zero shown

The Same Temperatures with Absolute Zero Shown


The same temperatures on a ratio scale rankine f 459 6

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


The same temperatures on a ratio scale kelvin c 273 15

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


Discrete vs continuous variables

Discrete vs. ContinuousVariables

  • discrete: separate, whole number values

    • EXAMPLE: number of pets

  • continuous: continuum including fractional values

    • EXAMPLE: height


Real limits

Real Limits

  • 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.

    • measured score = 65 inches

    • real limits: 64.5-65.5 inches


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