Case Study

Diagnose how the single score of 2020 impacts the range calculation. Clarify what false impression the resulting range of 8080 gives about the group, and describe the actual consistency of the majority of the students.

Case context: A psychology instructor analyzes the exam scores of a class. The majority of the students scored between 9090 and 100100, which would yield a narrow range of 1010. However, one student scored a 2020. Calculating the range for the entire class results in a value of 8080. The instructor wants to understand why this range value is misleading.

Question: Diagnose how the single score of 2020 impacts the range calculation. Clarify what false impression the resulting range of 8080 gives about the group, and describe the actual consistency of the majority of the students.

Sample answer: The score of 2020 acts as an outlier that dramatically increases the range from 1010 to 8080. This inflated range of 8080 is misleading because it gives the false impression that the entire class's scores are highly variable. In reality, the class is highly consistent, as almost all students scored between 9090 and 100100, with only a single student deviating from the rest.

Key points:

  • The score of 2020 acts as an outlier that distorts the range.
  • The range is inflated from 1010 to 8080 due to this single score.
  • The range of 8080 falsely suggests the entire class's scores are highly variable.
  • The majority of the class scored consistently between 9090 and 100100.

Rubric: The response must identify the score of 2020 as an outlier that inflates the range. It must explain that this inflated range incorrectly suggests high variability among the entire class, whereas the majority of the class actually performed consistently within a narrow range.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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