This problem demonstrates a possible (though rare) situation that can occur with group comparisons.
The groups are sections and the dependent variable is an exam score.
This data set can be downloaded in serial format with this link: Download CSV
Run a one-factor ANOVA (fixed effect) with . Report the F-ratio to 3 decimal places and the P-value to 4 decimal places.
What is the conclusion from the ANOVA?
Calculate the group means for each section:
Section 1:
Section 2:
Section 3:
Report means accurate to 2 decimal places.
Conduct 3 independent sample t-tests for each possible pair of sections. (Though we will see later that it might not be appropriate, retain the significance level .) Report the P-value (accurate to 4 decimal places) for each pairwise comparison.
Compare sections 1 & 2:
Compare sections 1 & 3:
Compare sections 2 & 3:
Based on these comparisons, which pair of groups have statistically significantly different means?
Thought for reflection: What do the results of the pairwise comparisons suggest about the original conclusion from the ANOVA?
Section 1 | Section 2 | Section 3 |
---|---|---|
67 | 54.9 | 55.6 |
76.4 | 57.3 | 65.6 |
52.3 | 50 | 57.3 |
60.1 | 49.1 | 66.4 |
59 | 75.6 | 73 |
62.1 | 72 | 63.8 |
72.7 | 35.9 | 67 |
70.7 | 33.3 | 70.5 |
67.9 | 60.1 | 62.5 |
Run a one-factor ANOVA (fixed effect) with . Report the F-ratio to 3 decimal places and the P-value to 4 decimal places.
What is the conclusion from the ANOVA?
Calculate the group means for each section:
Section 1:
Section 2:
Section 3:
Report means accurate to 2 decimal places.
Conduct 3 independent sample t-tests for each possible pair of sections. (Though we will see later that it might not be appropriate, retain the significance level .) Report the P-value (accurate to 4 decimal places) for each pairwise comparison.
Compare sections 1 & 2:
Compare sections 1 & 3:
Compare sections 2 & 3:
Based on these comparisons, which pair of groups have statistically significantly different means?
Thought for reflection: What do the results of the pairwise comparisons suggest about the original conclusion from the ANOVA?