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In the calorie-estimate and weight study (), Pearson's was calculated as . Analyze why the researcher compared the absolute value of the correlation coefficient () rather than the raw value () to the critical value () when determining significance.
Question: In the calorie-estimate and weight study (), Pearson's was calculated as . Analyze why the researcher compared the absolute value of the correlation coefficient () rather than the raw value () to the critical value () when determining significance.
Sample answer: Because the researcher conducted a two-tailed test, the critical region is split between both positive and negative directions, corresponding to critical values of . Using the absolute value () simplifies the comparison to the positive critical value () and is mathematically equivalent to confirming that the raw coefficient of falls within the non-significant range between and .
Key points:
- Explain that a two-tailed test establishes critical boundaries in both directions (i.e., ).
- Explain that using the absolute value allows a direct comparison to the positive critical value.
- Explain that checking if the absolute value is less than the critical value is equivalent to checking if the raw coefficient falls between the negative and positive critical values.
Rubric: The answer should analyze that a two-tailed test has two critical values () and that comparing the absolute value of the correlation coefficient () to the critical value () correctly determines whether the sample correlation falls within the rejection region in either direction.
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Research Methods in Psychology - 4th American Edition @ KPU
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