Case Study

Explain how the student should calculate the standard deviation from their calculated variance of 3.503.50, and clarify the mathematical relationship between the variance and the standard deviation.

Case context: A student is analyzing participant scores for a psychology study. The student calculates that the sum of the squared differences from the mean is 2828 for 88 scores. They correctly calculate a variance of 3.503.50 by dividing 28/828 / 8, but they are confused about how to find the standard deviation and how it relates to the variance.

Question: Explain how the student should calculate the standard deviation from their calculated variance of 3.503.50, and clarify the mathematical relationship between the variance and the standard deviation.

Sample answer: The student should calculate the standard deviation by taking the square root of the variance (3.503.50), which gives 3.50=1.87\sqrt{3.50} = 1.87. Mathematically, the standard deviation is defined as the square root of the variance.

Key points:

  • Explain that the standard deviation is the square root of the variance.
  • Calculate the standard deviation as 3.50=1.87\sqrt{3.50} = 1.87.
  • Demonstrate comprehension of the relationship between variance and standard deviation.

Rubric: The response must explain that the standard deviation is the square root of the variance, and show the correct calculation of 3.50=1.87\sqrt{3.50} = 1.87 based on the student's variance of 3.503.50.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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