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Case Study

Based on the principles of psychological measurement, explain why Dr. Lopez's 20-item survey will likely produce more reliable scores than the single question. Furthermore, what is the purpose of calculating Cronbach's α\alpha for her new survey?

Case context: Dr. Lopez is developing a questionnaire for measuring financial responsibility among college students. Initially, she considers asking a single question: 'How financially responsible are you on a scale of 1 to 10?' However, she decides to create a 20-item survey instead, covering topics like budgeting, saving, and paying bills on time. After collecting the data, she analyzes the new survey using Cronbach's α\alpha.

Question: Based on the principles of psychological measurement, explain why Dr. Lopez's 20-item survey will likely produce more reliable scores than the single question. Furthermore, what is the purpose of calculating Cronbach's α\alpha for her new survey?

Sample answer: The 20-item survey will likely produce more reliable scores because human responses to single items can be influenced by irrelevant factors, such as momentarily misinterpreting a question or making a minor error. By summing or averaging responses across 20 items, these random errors tend to cancel each other out. Calculating Cronbach's α\alpha allows Dr. Lopez to assess the internal consistency of her multiple-item measure, ensuring that the 20 items relate to one another appropriately.

Key points:

  • Recognizes that responses to a single question can be distorted by irrelevant factors or minor errors.
  • Explains that aggregating (summing or averaging) multiple items allows these errors to cancel each other out.
  • Concludes that this canceling-out effect leads to more reliable scores overall.
  • Identifies that Cronbach's α\alpha or a split-half correlation is customary to assess the measure's internal consistency.

Rubric: The response should explain that averaging or summing multiple items reduces the impact of minor errors or misinterpretations because they cancel each other out, thereby increasing reliability. It must also correctly identify that Cronbach's α\alpha is used to evaluate the internal consistency of the multiple-item measure.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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