Valid CFA-Level-I Dumps shared by ExamDiscuss.com for Helping Passing CFA-Level-I Exam! ExamDiscuss.com now offer the newest CFA-Level-I exam dumps, the ExamDiscuss.com CFA-Level-I exam questions have been updated and answers have been corrected get the newest ExamDiscuss.com CFA-Level-I dumps with Test Engine here:
To estimate the average length of their employee's telephone calls, FoneJack, Inc. randomly sampled 25 employee phone calls. If the sample mean was 1.3 minutes and the population can be assumed normal with a standard deviation of 0.3 minutes then a 90% confidence interval for the phone calls is ______.
Correct Answer: A
For a 90% confidence interval we find z(0.05), the cut-off for the top 5% of the normal distribution. Looking up 0.95 in the middle of the table the reading to the row/column values, we get 1.645. Working with the formula for E (see top right) we get E = 0.1. So, the 90% confidence interval is 1.3 - 0.1 m 1.3 + 0.1 or 1.2 m 1.4.