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**CFA Practice Question**

The population of potatoes harvested during a year is very large (many millions). Suppose potato weights have a lognormal distribution. The mean weight of a potato is 0.2511 lbs, and the standard deviation is 0.0752 lbs. Consider a sample of size 100. Prior to the sample being taken, the mean of the sample is a random variable. What is the standard deviation of this random variable?

A. 0.029258

B. 0.075200

C. 0.006267

**Explanation:**From CLT, we know the sample mean is normally distributed around the population mean.

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**User Contributed Comments**
5

User |
Comment |
---|---|

Marleni |
how do you get .006267? |

chantal |
All I can think of is that the population mean will have a much lower standard of deviation simply because it has no sample error. Assuming a 5% max error, ie 2.5% on each side you will get a standard deviation of 0.0063. ??? |

kazec1 |
Shouldn't the std simply be 0.0752/10?? |

safash |
So I'm assuming everybody who attempted this got it wrong!!!!! |

seanj951 |
In what way is that an explanation for how to get 0.006267? |