Question

In a study on the effect of an oral rinse on plaque buildup on teeth, twelve people whose teeth were thoroughly cleaned and polished were randomly assigned to two groups of six 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 the rinse contained no antiplaque agent. A measure of plaque buildup was recorded at 14 days with means and standard deviations for the two groups shown in the table.

	Control Group	Antiplaque Group
Sample Size	6	6
Mean	1.28	0.73
Standard Deviation	0.34	0.34

(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 = 0.05.

State the test statistic. (Round your answer to three decimal places.)

t =

State the rejection region. (If the test is one-tailed, enter NONE for the unused region. Round your answers to three decimal places.)

t >  

t<

Answer 1

a) H0: not effectiveness of the antiplaque oral rinse.

H1: the effectiveness of the antiplaque oral rinse.

b) Test Statistic:

c) Reject Region: Reject H0 if t>1.812

since t value is 2.802 > 1.812 so we reject H0

Thus we conclude that the effectiveness of the antiplaque oral rinse.