Question

Researchers conducted a medical study to find out if treating a sinus infection with an antibiotic reduced the length of the sinus infection. The study included 241 patients who were diagnosed with a sinus infection. There were 113 patients randomly assigned to receive the antibiotic. The remaining patients received sugar pills. The patients were contacted regularly to find out when each patient stopped having sinus infection symptoms. The results of the study are presented in the table below.

	TREATMENT
Length of Sinus Infection	Sugar Pill	Antibiotic	Total
Less than 10 Days	80	80	160
10 or More Days	48	33	81
Total	128	113	241

1. What is the probability that a randomly selected patient received the antibiotic and the   sinus infection lasted more than 10 days?
   1. 33/241 = 0.137
   2. 33/113 = 0.292
   3. 33/81 = 0.407

2. What is the probability that a randomly selected patient who received the antibiotic had a sinus infection that lasted more than 10 days?

a. 33/241 = 0.137

b. 33/113 = 0.292

c. 33/81 = 0.407

3. Which of the following is a reasonable approximation for the chance that a sinus infection would last 10 or more days for a patient who received the antibiotic?

a. About a 1 in 7 chance

b. About a 2 in 7 chance

c. About a 3 in 7 chance

4. Imagine that 1000 patients with sinus infections were treated with the antibiotic. Approximately, how many of them would you expect to stop having sinus infection symptoms in less than 10 days?

a. 70

b. 650

c. 708

d. 950

Answer 1