Question

41. W Fewer young people are driving. In 1983, 87% of 19-year-olds had a driver's license. Twenty-five years later that percentage had dropped to 75% (University of Michigan Transportation Research Institute website, April 7, 2012). Suppose these results are based on a random sample of 1200 19-year-olds in 1983 and again in 2008. a. At 95% confidence, what is the margin of error and the interval estimate of the number of 19-year-old drivers in 1983? b. At 95% confidence, what is the margin of error and the interval estimate of the number of 19-year-old drivers in 2008?

Answer 1

LE3 Margin of exor = 2*12* |P(-2) da 1-0.95 = 0.05 1200 2012 = 20.0512 = 20.025 = 1.96 ca) At 95% confidence, in 1983 P=0.87 and n = 1200 q - 1-P = 1 -0.87 = 0.13 E = Margin of error = 1.96* 0-87 *0:13 - 0.01902 (I = È IE = 0.87 + 0 0.0190 = 0.051, 0.889 (b) 954. confidence internal (CI) in dood p = 0.75 q- 1-P = 1-0.75 = 0.25 sor= 1.96 * 10.75*0.25 V 1200 = 0.0245 CI = PEE = 0.75 + 0.0245 = 0.7855, 0.7745 cs Scanned with CamScanner