In a study of treatments for very painful"cluster" headaches, 149 patients were treated with oxygen and 140 other patients were given a placebo consisting of ordinary air. Among the 149 patients in the oxygen treatmentgroup, 125 were free from headaches 15 minutes after treatment. Among the 140 patients given theplacebo, 26 were free from headaches 15 minutes after treatment. Use a 0.05 significance level to test the claim that the oxygen treatment is effective. Complete parts(a) through(c) below.

a. Test the claim using a hypothesis test.

Consider the first sample to be the sample of patients treated with oxygen and the second sample to be the sample of patients given a placebo. What are the null and alternative hypotheses for the hypothesistest?

Identify the test statistic.

z=

(Round to two decimal places asneeded.)

Identify theP-value.

p-value =

(Round to three decimal places asneeded.)

What is the conclusion based on the hypothesistest?

b. Test the claim by constructing an appropriate confidence interval.

The 98% confidence interval is

________

(Round to three decimal places asneeded.)

c. Based on theresults, is the oxygen treatmenteffective?

A.

The results suggest that the oxygen treatment is not effective in curing"cluster" headaches because the cure rates appear to be the same.

B.

The results suggest that the oxygen treatment is effective in curing"cluster" headaches.

Your answer is correct.

C.

The results suggest that the oxygen treatment is not effective in curing"cluster" headaches because the cure rate for the oxygen treatment appears to be lower than that of the placebo.

D.

The results are inconclusive.