In: Statistics and Probability
The following data were obtained from a study using two separate toothpastes. You used them on the last homework in R. Now you will work with them to compute the ANOVA by hand. Subjects in group I received a fluoride-supplemented toothpaste for one year while those in group II used one without added fluoride. At the end of the trial period the number of cavities needing to be filled was used as the dependant variable. A) Compute an analysis of variance (ANOVA) with = 0.05 determine whether the data indicate a significant difference between the two treatments. To do this you will need to compute the sum of squares (SS) between groups and the SS within groups on your way to computing the F-ratio. (Be sure to show your work.) B) Assemble your ANOVA calculations into the standard ANOVA table and type it below. C) Compute a t-test for independent groups with = 0.05 determine whether the data indicate a significant difference between the two treatments. C) Check that your results confirm the general relationship between F-ratio (ANOVA) and the t-statistic. Comparing your F-ratio from part a to your t-statistic from part b you should find that F = t2. Why is this so?
Treatments |
||
I (fluoride) |
II (no fluoride) |
|
0 |
10 |
|
1 |
4 |
|
7 |
10 |
|
4 |
4 |