College X is concerned about their employees making use of their email for non-business purposes. A random sample of 400 e-mails discovered 80 messages that were not business related. The 90%
Confidence interval for the population proportion is:
A) 0.167 to 0.233
B) 0.161 to 0.239
C) 0.148 to 0.252
D) 0.186 to 0.254
E) 0.179 to 0.261

Question

Quizplus · Accepted Answer

The sample proportion is 80/400 = 0.2. The standard error is sqrt[(0.2)(0.8)/400] = 0.02. For a 90% confidence interval, the z-score is approximately 1.645. The margin of error is 1.645 * 0.02 = 0.0329. The confidence interval is 0.2 ± 0.0329, which is approximately 0.167 to 0.233.

College X Is Concerned About Their Employees Making Use of Their