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

  • 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

  • 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

  • Numbers classify into groups.

  • Math, other than counting, is not meaningful.

  • EXAMPLES:

    • gender

    • hair color


Ordinal Scale

  • Numbers are rank orders.

  • Most mathematical operations are not meaningful.

  • EXAMPLES:

    • order of finish in a race

    • class rank


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

  • 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


The Same Temperatures on Another Interval Scale


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 (Kelvin = C + 273.15)


Discrete vs. ContinuousVariables

  • discrete: separate, whole number values

    • EXAMPLE: number of pets

  • continuous: continuum including fractional values

    • EXAMPLE: height


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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