Chapter 10.4, Problem 10.25E

Healthy Teeth Jan Lindhe conducted a studyon the effect of an oral antiplaque rinse on plaquebuildup on teeth.⁶Fourteen people whose teeth werethoroughly cleaned and polished were randomlyassigned to two groups of seven subjects each. Bothgroups were assigned to use oral rinses (no brushing)for a 2-week period. Group 1 used a rinse thatcontained an antiplaque agent. Group 2, the controlgroup, received a similar rinse except that, unknown to the subjects, the rinse contained no antiplaque agent. Aplaque index x, a measure of plaque buildup, wasrecorded at 14 days with means and standard deviations for the two groups shown in the table.

1. State the null and alternative hypotheses that shouldbe used to test the effectiveness of the antiplaqueoral rinse.
2. Do the data provide sufficient evidence to indicatethat the oral antiplaque rinse is effective? Test using $\alpha =\mathrm{.05.}$
3. Find the approximate p-value for the test.