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Based on the researcher's scenario, explain why they should use Fisher's Least Significant Difference (LSD) test for their post hoc pairwise comparisons instead of running multiple standard -tests, and describe what error they are preventing.
Case context: A psychology researcher conducts a study comparing the effectiveness of three different study environments on student concentration. After running a one-way ANOVA, they find a statistically significant overall result. The researcher wants to compare the means of each environment pair to see which ones differ, but they are concerned about the risk of making a Type I error.
Question: Based on the researcher's scenario, explain why they should use Fisher's Least Significant Difference (LSD) test for their post hoc pairwise comparisons instead of running multiple standard -tests, and describe what error they are preventing.
Sample answer: The researcher should use Fisher's LSD because it is a modified -test procedure designed for post hoc comparisons after a significant one-way ANOVA. If the researcher ran multiple standard -tests, the compounded risk of making a Type I error would increase. Fisher's LSD mathematically controls this compounded risk of making a Type I error (mistakenly rejecting a true null hypothesis) while allowing the researcher to evaluate differences between specific pairs of group means.
Key points:
- Fisher's LSD is designed specifically for post hoc comparisons after a significant one-way ANOVA.
- Running multiple standard -tests increases the compounded risk of making a Type I error.
- A Type I error is mistakenly rejecting a true null hypothesis.
- Fisher's LSD mathematically controls this compounded risk.
Rubric:
- Explains that Fisher's LSD is suitable because it is designed for post hoc comparisons following a significant one-way ANOVA (3 points). 2. Explains that multiple standard -tests increase the compounded risk of making a Type I error (4 points). 3. Correctly defines a Type I error as mistakenly rejecting a true null hypothesis and states that Fisher's LSD mathematically controls this risk (3 points).
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Research Methods in Psychology - 4th American Edition @ KPU
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