A large national company is considering negotiating cellular phone rates for its employees.The Human Resource department would like to estimate the proportion of its employee population who own an Apple iPhone.A random sample of size 250 is taken and 40% of the sample own and iPhone.The 90% confidence interval to estimate the population proportion is ____.
A) 0.35 to 0.45
B) 0.34 to 0.46
C) 0.37 to 0.43
D) 0.39 to 0.41
E) 0.40 to 0.45

Question

Quizplus · Accepted Answer

The sample proportion is 0.40, and the sample size is 250. The standard error of the proportion is sqrt(0.40 * 0.60 / 250) = 0.032. The 90% confidence interval is 0.40 +/- 1.645 * 0.032 = (0.35, 0.45).

A Large National Company Is Considering Negotiating Cellular Phone Rates