In: Statistics and Probability
Toothpaste The table shows the costs per ounce (in dollars) for a sample of toothpastes exhibiting very good stain removal, good stain removal, and fair stain removal. At α = 0.05, can you conclude that at least one mean cost per ounce is different from the others?
Very Good |
.47 |
.49 |
.41 |
.37 |
.48 |
.51 |
Good |
.60 |
.64 |
.58 |
.75 |
.46 |
|
Fair |
.34 |
.46 |
.44 |
.60 |
Null Hypothesis, Ho:
There is no significant difference in the means cost per ounce for toothpaste exhibiting very good stain removal, good stain removal, and fair stain removal i.e.
Alternative Hypothesis, Ha:
There exists at least toothpaste for which the mean cost per ounce is significantly different i.e. for at least one
Test Statistics: Under Ho,
where k = number of groups = 3 and,
n = number of observations = 15
Calculations:
Treatment Groups | ni | si | |
Very Good | 6 | 0.455 | 0.0536 |
Good | 5 | 0.606 | 0.1048 |
Fair | 4 | 0.46 | 0.1071 |
So,
and ,
Decision:
Since, p-value = 0.02951 < , so we reject the Null Hypothesis at 5% level of significance.
Conclusion:
There exists at least toothpaste for which the mean cost per ounce is significantly different i.e. for at least one