A researcher conducted an experiment testing the effectiveness of three types of air fresheners (Stop Stank, Fresh Breeze, and Snorp) on odor control. The experiment was conducted in three identical testing rooms. A precise amount of the same odor was released into each room. Thirty participants were randomly assigned to one of the three groups. Once the participants were in the rooms, one of the three types of air fresheners was released into the room. Participants waited in the room for three minutes. Then participants were asked to rate the odor level of the room on a 10-point scale ranging from 0 (no unpleasant odor) to 10 (strong unpleasant odor).
| Stop Stank | Fresh Breeze | Snorp |
| 1 | 1 | 6 |
| 3 | 2 | 7 |
| 2 | 3 | 8 |
| 1 | 2 | 7 |
| 2 | 4 | 8 |
| 1 | 1 | 6 |
| 2 | 2 | 8 |
| 4 | 1 | 7 |
| 2 | 2 | 8 |
| 1 | 1 | 6 |
| Stop Stank | Fresh Breeze | Snorp | |
| Mean | 1.9 | 1.9 | 7.1 |
| SD | 0.99 | 0.99 | 0.88 |
| Stop Stank vs. Fresh Breeze | Fresh Breeze vs. Snorp | Snorp vs. Stop Stank | |
| Mean difference | 0.00 | -5.2 | 5.2 |
| p value | 1.0 | <0.0005 | <0.0005 |
The one-way ANOVA is to test the effectiveess of three types of air fresheners. The aveage scores of odor level for the groups named Stop Stank, Fresh Breeze and Snorp are 1.9, 1.9 and 7.1, respectively.
The significant main effect for odor score is F(2,27) = 98.526, the p value is less than 0.0005 so we reject the null hypothesis.
So we can conclude that at least one of the air fresheners is not equal to their odor scores.
The Tukey test showed that there is no significant difference in the scores between Stop Stank (M=1.9) and Fresh Breeze (M=1.9).
The Tukey test showed there is a significant difference in the scores between Stop Stank (M=1.9) and Snorp (M=7.1).
The Tukey test showed there is a significant difference in the scores between Fresh Breeze (M=1.9) and Snorp (M=7.1)
