Case Study

Explain why the new mean of 1,4451,445 milliseconds is not a suitable representation of typical behavior in this distribution, and explain which alternative measure of central tendency the researcher should prefer and why.

Case context: A cognitive psychology researcher is analyzing a pilot dataset of simple reaction times from a participant. The initial four trials yielded scores of 200200, 250250, 280280, and 250250 milliseconds, with a mean of 245245 milliseconds. However, on a subsequent trial, the participant temporarily lost focus, resulting in an extreme outlier score of 5,0005,000 milliseconds. When this trial is added, the mean rises to 1,4451,445 milliseconds.

Question: Explain why the new mean of 1,4451,445 milliseconds is not a suitable representation of typical behavior in this distribution, and explain which alternative measure of central tendency the researcher should prefer and why.

Sample answer: The new mean of 1,4451,445 milliseconds is not a suitable representation because a single extreme outlier (5,0005,000 milliseconds) has skewed the distribution, making the mean higher than 8080% of the scores. It fails to reflect the typical reaction times of the participant (which cluster between 200200 and 280280 milliseconds). The researcher should prefer the median instead, as the median is less sensitive to extreme outliers and better represents typical behavior in highly skewed distributions.

Key points:

  • The new mean of 1,4451,445 milliseconds is greater than 8080% of the scores.
  • The mean fails to represent typical behavior in the skewed distribution.
  • Researchers prefer the median over the mean for highly skewed distributions.

Rubric: The response should demonstrate comprehension by explaining that: 1) The new mean is unrepresentative because it is larger than 8080% of the scores due to the extreme outlier. 2) The mean fails to reflect the typical clustering of reaction times. 3) The median should be preferred for highly skewed distributions to better represent typical behavior.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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