Jan Lindhe conducted a study16 on the effect of an oral antiplaque rinse on plaque buildup on teeth. Fourteen subjects, whose teeth were thoroughly cleaned and polished, were randomly assigned to two groups of seven subjects each. Both groups were assigned to use oral rinses (no brushing) for a 2-week period. Group 1 used a rinse that contained an antiplaque agent. Group 2, the control group, received a similar rinse except that, unknown to the subjects, the rinse contained no antiplaque agent. A plaque index y, a measure of plaque buildup, was recorded at 4, 7, and 14 days. The mean and standard deviation for the 14-day plaque measurements for the two groups are given in the following table:
Control Group Antiplaquc Group
Sample size 7 7
Mean 1.26 .78
Standard deviation .32 .32
a. State the null and alternative hypotheses that should be used to test the effectiveness of the antiplaque oral rinse.
b. Do the data provide sufficient evidence to indicate that the oral antiplaque rinse is effective? Test using α = .05.
c. Bound or find the p-value for the test.