Essay

Describe the step-by-step mathematical procedure used to compute the standard deviation (SDSD) as represented by the formula: SD=(XM)2NSD = \sqrt{\frac {\sum (X-M)^2}{N}}.

Question: Describe the step-by-step mathematical procedure used to compute the standard deviation (SDSD) as represented by the formula: SD=(XM)2NSD = \sqrt{\frac {\sum (X-M)^2}{N}}.

Sample answer: To calculate the standard deviation using this formula, you must first find the difference between each individual score (XX) and the mean of the dataset (MM). Second, square each of those individual differences. Third, find the mean of these squared differences by summing them and dividing by the total number of scores (NN). Finally, take the square root of that mean.

Key points:

  • Find the difference between each score (XX) and the mean (MM).
  • Square each of the calculated differences.
  • Calculate the mean of the squared differences.
  • Find the square root of the mean of the squared differences.

Rubric: The response must recall all four steps in the correct order: (1) subtracting the mean from each score, (2) squaring the resulting differences, (3) calculating the mean of the squared differences (summing and dividing by NN), and (4) taking the square root of that mean.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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