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Case Study

Based on the instructor's graph, diagnose the specific type of distribution shape present. Explain how the clustering of scores and the direction of the tail in this specific scenario justify your diagnosis.

Case context: A psychology instructor plots the final exam grades of 200 introductory psychology students on a frequency distribution graph. The instructor observes a distinct asymmetrical shape: a prominent peak appears on the right side of the graph because the vast majority of students scored very high (between 85% and 100%). Meanwhile, a long tail of scores trails off toward the lower end of the scale on the left side, representing a small number of students who scored poorly.

Question: Based on the instructor's graph, diagnose the specific type of distribution shape present. Explain how the clustering of scores and the direction of the tail in this specific scenario justify your diagnosis.

Sample answer: The exam scores represent a negatively skewed distribution. This is justified because the majority of the students' grades are clustered at the higher end of the scale, which creates the prominent peak on the right side of the distribution. The small number of low scores creates a long tail that trails off toward the lower end on the left, which is the defining visual characteristic of a negatively skewed distribution.

Key points:

  • Diagnose the shape as a negatively skewed distribution.
  • Acknowledge that the prominent peak on the right is caused by most scores clustering at the higher end.
  • Explain that the long tail pointing to the left is formed by the trailing off of lower scores.

Rubric: Full credit is awarded if the student correctly identifies the distribution as negatively skewed and explains that the diagnosis is based on the high-score clustering (peak on the right) and the low-score trailing (tail on the left).

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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