Case Study

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 (MSBMS_B) of 5,971.88 and a within-groups mean square (MSWMS_W) of 602.23, which results in an FF ratio of 9.92. With 22 and 2121 degrees of freedom, the critical value of FF is 3.467, and the corresponding pp-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 FF ratio of 9.92 is greater than the critical value of 3.467 (or because the obtained pp-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 FF score of 9.92 to the critical value of 3.467 (or comparing the pp-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 F>3.467F > 3.467 or p<.05p < .05) and state the correct interpretation regarding the difference among population means.

0

1

Updated 2026-05-27

Contributors are:

Who are from:

Tags

KPU

Research Methods in Psychology - 4th American Edition @ KPU

Related