Essay

Based on the provided textbook example of computing the standard deviation for the scores 3,5,4,2,7,6,53, 5, 4, 2, 7, 6, 5, and 88 (with a mean of 55), outline the step-by-step mathematical process required to calculate the standard deviation from these raw scores, and state the final numerical values of the variance and standard deviation.

Question: Based on the provided textbook example of computing the standard deviation for the scores 3,5,4,2,7,6,53, 5, 4, 2, 7, 6, 5, and 88 (with a mean of 55), outline the step-by-step mathematical process required to calculate the standard deviation from these raw scores, and state the final numerical values of the variance and standard deviation.

Sample answer: To calculate the standard deviation, first determine the difference between each of the eight scores (3,5,4,2,7,6,53, 5, 4, 2, 7, 6, 5, and 88) and the mean of 55. Second, square each of these differences to make all values positive. Third, find the mean of these squared differences, which is the variance (calculated as 28/8=3.5028 / 8 = 3.50). Finally, take the square root of the variance to find the standard deviation, which is 3.50=1.87\sqrt{3.50} = 1.87.

Key points:

  • Subtract the mean (55) from each raw score to find the differences.
  • Square each individual difference to make all values positive.
  • Compute the mean of the squared differences to find the variance (3.503.50).
  • Take the square root of the variance to determine the standard deviation (1.871.87).

Rubric: Student response must correctly recall the four steps of the calculation: 1) subtracting the mean from each score, 2) squaring each difference, 3) finding the mean of the squared differences (variance), and 4) taking the square root of the variance (standard deviation). The response must also state the variance is 3.503.50 and the standard deviation is 1.871.87.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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