CFA Practice Question

There are 434 practice questions for this study session.

CFA Practice Question

For a normal population with s unknown, a sample of size n = 21 yields a sample mean of 32 and a sample standard deviation of 3. At a 90% confidence interval for m is ______ (to nearest 0.01).

A. 31.13 < m < 32.87
B. 30.35 < m < 33.65
C. 30.87 < m < 33.13
Correct Answer: C

Because s is unknown we use the t-distribution. We work with E as shown below. The a level is 0.1/2 = 0.05 and the degrees of freedom is 21 - 1 or 20. The table value is 1.725. E is 1.13 and the confidence interval is 30.87 < m < 33.13.

User Contributed Comments 2

User Comment
PSVC How do we know when to use the one sided/two sided tails?
ravinram Confidence interval is always 2 sided
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