Measurement
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Measurement. 2011, 9, 8. Today’s Topics. Scale of measurement* Measurement reliability* Measurement validity**. Measuring a Variable. Nominal Scale: Mutually exclusive categories without order Political party: Democrat, Republican Gender: Male, Female

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Presentation Transcript
Measurement

Measurement

2011, 9, 8


Today s topics
Today’s Topics

  • Scale of measurement*

  • Measurement reliability*

  • Measurement validity**


Measuring a variable
Measuring a Variable

  • Nominal Scale: Mutually exclusive categories without order

    • Political party: Democrat, Republican

    • Gender: Male, Female

  • Ordinal Scale: Categories with rank order

    • Social class: Upper, middle, lower

    • Education level: High school, college, graduate

  • Interval-Ratio Scale: the intervals between two consecutive categories are the same size

    • Temperature

    • Income

arbitrary zero

natural zero


Critical thinking question
Critical Thinking Question

  • What is the difference between measurement unit and unit of analysis?


Reliability
Reliability

  • An indication of the consistency or stability of a measuring instrument

    • Free of random error

  • Question 1: You took an IQ test twice in one day. In the morning, you received a below-average score of 85. So took it again in the afternoon. This time, you received a above-average score of 120. What is the problem of the IQ test?

  • Question 2: I tend to be late because my watch is set 10 minutes behind. Is my watch reliable? What is the problem of the watch?


Validity accuracy
Validity (Accuracy)

  • Whether a measure is truthful or genuine

    • Free of random error: Same result over and over

    • Free of systematic bias: Accurate result

    • Measures what it is designed to measure

      • Need for Achievement scale


Lab 3 recap
Lab 3 Recap

  • Scale of measurement

    • Nominal scale

    • Ordinal scale

    • Interval-ratio scale

  • Reliability: Free of random error

  • Validity / Accuracy:

    • Free of random error

    • Free of systematic bias

    • Measures what it is supposed to measure


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