Case Study

Based on this scenario, diagnose the student's errors and explain the correct conceptual method for finding the median of both the original seven-score dataset and the new eight-score dataset.

Case context: A student researcher is examining response times in a cognitive psychology task. They collect the scores of seven participants: 88, 44, 1212, 1414, 33, 22, and 33 seconds. Without sorting the data, the student identifies the middle score in the raw list (1414) as the median. Later, when an eighth participant is added with a score of 1515, the student incorrectly calculates the median by taking the average of the raw list's middle values.

Question: Based on this scenario, diagnose the student's errors and explain the correct conceptual method for finding the median of both the original seven-score dataset and the new eight-score dataset.

Sample answer: The student's primary error is failing to rearrange the scores from lowest to highest before locating the median. Conceptually, the median must divide the ordered distribution into two equal halves. For the seven scores, once arranged to (22, 33, 33, 44, 88, 1212, 1414), the middle score is 44. When the score of 1515 is added to create an even dataset, the ordered scores are (22, 33, 33, 44, 88, 1212, 1414, 1515). There are two middle values, 44 and 88, meaning the median must be the value halfway between them, which is 66.

Key points:

  • Identify the error of not sorting the raw dataset.
  • Order the raw scores to (22, 33, 33, 44, 88, 1212, 1414) and locate the median of 44.
  • Identify that adding a score of 1515 creates an even number of scores.
  • Find the two middle values (44 and 88) of the ordered even dataset and calculate the median (66) halfway between them.

Rubric: Grading criteria: 1. Clearly identify that the student failed to sort the scores before locating the middle value. 2. Correctly describe the sorting step and identify the correct median of 44 for the odd dataset. 3. Correctly describe the method for an even dataset, identifying the two middle values as 44 and 88, and finding the value halfway between them (66).

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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