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Based on this scenario, explain why the mean reaction time of 1,445 ms is not an accurate representation of the group's performance. Support your explanation by referencing how the new mean compares to the individual scores in the dataset.
Case context: A student researcher is analyzing reaction time data from a pilot study. The initial four participants have reaction times of ms, ms, ms, and ms, which produces a mean of ms. When a fifth participant's score of 5,000 ms (suspected to be caused by participant inattention) is added, the mean increases to 1,445 ms.
Question: Based on this scenario, explain why the mean reaction time of 1,445 ms is not an accurate representation of the group's performance. Support your explanation by referencing how the new mean compares to the individual scores in the dataset.
Sample answer: The new mean of 1,445 ms is not accurate because it is heavily skewed by a single extreme outlier (5,000 ms). The calculated mean is higher than of the actual reaction times in the dataset (, , , and ms are all far below 1,445 ms). Therefore, the mean is pulled upwards and does not represent the behavior of any typical participant.
Key points:
- The single outlier of 5,000 ms pulls the mean from ms to 1,445 ms.
- The new mean (1,445 ms) is larger than of the scores in the dataset.
- A measure of central tendency should represent typical behavior, but this mean is higher than almost all actual scores.
Rubric: Full credit is awarded if the student explains that the 5,000 ms outlier skews the mean, identifies that the mean of 1,445 ms is larger than of the scores in the dataset, and concludes that it fails to represent typical behavior.
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Research Methods in Psychology - 4th American Edition @ KPU
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Adding a single extreme outlier to a small dataset can pull the mean so far that it no longer accurately represents the typical behavior in the distribution.
In a study on reaction times, a researcher calculates a mean of 245 ms for a set of four participants (200, 250, 280, and 250 ms). If a fifth participant provides an outlier score of 5,000 ms, the mean drastically increases to 1,445 ms. Which statement best explains why this new mean is a poor representation of the 'typical' behavior in this dataset?
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Based on this scenario, explain why the mean reaction time of 1,445 ms is not an accurate representation of the group's performance. Support your explanation by referencing how the new mean compares to the individual scores in the dataset.
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