Question

A building manager installs sensors to see how often people turn off the lights when they leave a room. After a month, the manager has a sample size of 400, a sample mean of 47%, and a sample standard deviation of 4%. What is the confidence level for a confidence interval of 46.6% to 47.4%?

A. 68%
B. 85%
C. 99.7%
D. 95%

Answer 1

Answer: 95%

Explanation:

Answer 2

The answer is C.

The figures in your problem are inconsistent with the data.
The sample std deviation is not and cannot be .04 (4%).
the sample std dev is sqrt[(.47)(1-.47)/400]=.02495.
The margin of error from your CI is .474 -.47= .004 (very small).
This would represent .02495/.004= 6.24 std dev. from expected, which would have a very
high level of confidence (99.97.. %). Something is likely wrong with the figures in your problem.