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Measurement

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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Measurement

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  1. Measurement 2011, 9, 8

  2. Today’s Topics • Scale of measurement* • Measurement reliability* • Measurement validity**

  3. 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

  4. Critical Thinking Question • What is the difference between measurement unit and unit of analysis?

  5. 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?

  6. 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

  7. 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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