13. Cure for the Common Cold? An experiment was planned to compare the mean time (in days) to recover from a common cold for people given a daily dose of 4 milligrams (mg) of vitamin C versus those who were not.

Suppose that 35 adults were randomly selected for each treatment category and that the mean recovery times and standard deviations for the two groups were as follows:

a. If you want to show that the use of vitamin C reduces the mean time to recover from a common cold, give the null and alternative hypotheses for the test. Is this a one- or a two-tailed test?

b. Conduct the statistical test of the null hypothesis in part a and state your conclusion. Test using a 5.05.

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Sample Size Sample Mean Sample Standard Deviation No Vitamin Supplement 4 mg Vitamin C 35 35 6.9 5.8 2.9 1.2