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Based on this context, justify the researcher's decision to reject the null hypothesis and explain the meaning of this statistical decision in relation to the population mean calorie estimates of the three groups.
Case context: A health psychologist is comparing the calorie estimates of three distinct groups: psychology majors, nutrition majors, and professional dieticians. The researcher runs a one-way ANOVA and calculates a between-groups mean square () of 5,971.88 and a within-groups mean square () of 602.23, which results in an ratio of 9.92. With and degrees of freedom, the critical value of is 3.467, and the corresponding -value is .0009.
Question: Based on this context, justify the researcher's decision to reject the null hypothesis and explain the meaning of this statistical decision in relation to the population mean calorie estimates of the three groups.
Sample answer: The researcher's decision to reject the null hypothesis is statistically justified because the computed ratio of 9.92 is greater than the critical value of 3.467 (or because the obtained -value of .0009 is less than the standard .05 alpha level). Rejecting the null hypothesis means that there is sufficient statistical evidence to conclude that the population mean calorie estimates of the three groups are significantly different from one another, rather than being equal.
Key points:
- Compares the calculated score of 9.92 to the critical value of 3.467 (or comparing the -value of .0009 to the alpha level of .05) to justify rejecting the null hypothesis.
- Explains that rejecting the null hypothesis indicates the differences between the group means are not due to random chance alone.
- Concludes that the population mean calorie estimates for the three groups are significantly different.
Rubric: The response must contain a valid statistical justification comparing the computed statistic to its threshold (either or ) and state the correct interpretation regarding the difference among population means.
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Research Methods in Psychology - 4th American Edition @ KPU
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In the one-way ANOVA example comparing calorie estimates among three groups, why does the researcher reject the null hypothesis?
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In a health psychology study comparing calorie estimates among psychology majors, nutrition majors, and dieticians, a researcher calculates an ratio of 9.92 and finds the critical value to be 3.467. To evaluate the null hypothesis () at an alpha level of .05, the researcher determines that because the calculated statistic exceeds the critical value, the most appropriate statistical decision is to _____ the null hypothesis.
Match each ANOVA component from the calorie-estimate study to the specific aspect of variability it measures in the analysis.
After obtaining , , a health psychologist concludes: 'These results prove that professional dietary training causes more accurate calorie estimation.' A peer reviewer should judge this causal conclusion as _____, because the one-way ANOVA compared pre-existing groups without random assignment, making it impossible to rule out alternative explanations for the observed group differences.
Identify the three groups compared by the health psychologist in the provided one-way ANOVA example, recall their respective sample mean calorie estimates, and state the final statistical conclusion of the analysis.
Based on this context, justify the researcher's decision to reject the null hypothesis and explain the meaning of this statistical decision in relation to the population mean calorie estimates of the three groups.
Imagine a researcher replicates this study with new samples of the same size and finds a between-groups mean square () of 6,022.30 and a within-groups mean square () of 602.23. Using the critical value of 3.467, calculate the new ratio and state whether the researcher should reject the null hypothesis.