1. A bank wants to get new customers for their credit card. They try two different approaches in their marketing campaign. The first promises a "cash back" reward; the second promises low interest rates. A sample of 500 people are mailed the first brochure; of these, 100 get the credit card. A separate sample of 500 people are mailed the second brochure; 125 get the credit card. Are the two campaigns equally attractive to customers? Compute a 95% confidence interval for the difference in the two proportions.
A. (0.21, 0.29)
B. (-0.102, 0.002)
C. (-0.118, 0.018)
2. Drug sniffing dogs must be 95% accurate. A new dog is being tested and is right in 46 of 50 trials. Find a 95% confidence interval for the proportion of times the dog will be correct.
A. (0.845, 0.995)
B. (0.805, 0.973)
C. (0.819, 0.959)
3. A student believes that 20% of all students think pepperoni is their favorite pizza. He performs a test of hypothesis, H0: p = 0.2, having taken a sample of 200 students and finding that 52 think pepperoni is their favorite. He finds a p-value of 0.0338, so rejects the null at α = 0.05. He then computes a 95% confidence interval for the true proportion and finds it is (0.199, 0.321). He is confused. 20% is in the interval! What is the difference?
A. He made a mistake in one of his calculations.
B. The two use different values of p in computing the standard deviation.
C. He should have used the plus four confidence interval.