confidence .....interval

CFA Level I
#1

An analyst determined that the sample mean and variance for a normal distribution are 42 and 9, respectively. The 99% confidence interval for this random variable is closest to: Select exactly 1 answer(s) from the following: A. 15.0 to 69.0. B. 18.8 to 65.2. C. 34.3 to 49.7. D. 39.0 to 45.0. Thanks a lot

#2

C

#3

99% confidence interval = mean +/- 2,58SD

#4

thanks a lot

#5

c - for sure

#6

so it’s B : 42-2.58*9 = 18.8; 42+2.58*9=65.2

#7

got tricked by using variation of 9 instead of standard deviation of 3? It is C.

#8

yeah C. read the question very very carefully, i keep telling myself. they are sneaky.