Question: A study was done in Great Britain to assess the relationship between dietary intake of Vitamin C and smoking. Dietary intake of Vitamin C was obtained using 7-day diet records in which a subject recorded what was eaten, and a computer estimated nutrient intake. The following summary table gives the mean Vitamin C intake, the standard deviation, and the sample size. Do all tests at significance level 0.10.

Group Mean SD n

Nonsmokers 85 36 20

Smokers 68 28 30

(a) Test whether the two population variances are equal or not. State your hypothesis. What can you conclude?

(b) Based on the results in (a), use the appropriate t test to compare the mean for nonsmokers with the mean for smokers. State your hypothesis. Give the p-value, using the t table. What can you conclude?