A side effect of allergy medicines has been drowsiness, which make these medicines risky for industrial workers. A recent product, Hismanal is claimed by its manufacturer to be the first once-a-day, non-drowsy allergy medicine. The claim is based on a clinical study in which 1604 patients were given Hismanal and 1109 patients were given a placebo. Drowsiness was reported by 7.1% of the first group and by 6.4% of the second group. Are those percentages different at the .05 significance level?

Six months ago a survey was done for a national political leader. Of the sample of 1100, 56% indicated that they would vote for the leader. Last month, a survey of 800 similar voters indicated that only 46% would vote for the leader. But, are these percentages different at the 95% confidence level?

An insurance company is thinking of offering discounts in premiums to non-smokers. As part of the decision process, they looked at a study 200 men over 60 years old who were asked if they smoked at least one pack a day and if they had ever suffered from heart disease. Of the smokers, 19 suffered from heart disease, 37 did not. Of the non-smokers, 25 suffered from heart disease, 119 did not. Are these percentages different at the 90% confidence level?

A market researcher employed by a chain of no-wait oil-change service centers wants to know whether there is a difference between women and men in their use of the chain's services. A group of 500 people were asked whether they used the no-wait services. Of the females, 171 did not use the services, and 67 did. Among the males, 176 did not use the services, and 86 did. Are these percentages different at the .05 significance level?