In clinical trials of the allergy medicine Clarinex (5 mg), 3307 allergy sufferers were randomly assigned to either a Clarinex group or a placebo group. It was reported that 50 out of 1655 individuals in the Clarinex group and 31 out of 1652 individuals in the placebo group experienced dry mouth as a side effect of their respective treatments. Source: www.clarinex.com

(a) What type of experimental design is this?

(b) What is the response variable? Is it qualitative or quantitative?

(c) What is the explanatory variable? How many levels does the treatment have?

(d) The clinical trial was double-blind. What does this mean?

(e) Why is it important to have a placebo group?

(f) Does the sample evidence suggest that the proportion of individuals experiencing dry mouth is greater for those taking Clarinex than for those taking a placebo at the a = 0.05 level of significance?

(g) Do you believe the difference between the groups is practically significant?