- CFA Exams
- CFA Level I Exam
- Study Session 3. Quantitative Methods (2)
- Reading 10. Sampling and Estimation
- Subject 3. The Central Limit Theorem

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**CFA Practice Question**

True or False? If 100 random samples of size n were drawn and a 99% confidence interval for MU was computed for each, exactly 99 of these confidence intervals would contain within their limits the true population mean.

Correct Answer: False

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**User Contributed Comments**
10

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

Shalva |
an explanation please |

wulin |
key word is "exactly". |

jmelville |
The question doesn't tell you the sample size so you can't assume normal distribution. It only tells you the number of samples not the size. |

Mutsa |
sample size should be > 30 for it to app population mean. 100 is the number of samples, not sample size. |

dealer80 |
dear all 100 is the sample size and as wulin said above the key word is exactly |

dcfa |
100 is not the sample size, 100 is the number of samples drawn - n is the sample size |

geofin |
From the textbook: "If samples of the same size are drawn repeatedly from a population and a 90% confidence interval is calculated from each sample, then 90% of these intervals should contain the population mean as the number of samples goes to infinity." Since the number of samples in the question is only 100, then using "exactly" is incorrect. |

johntan1979 |
The error is 99% confidence interval does not mean 99% x 100. That's all and that's it. |

gill15 |
It means 99% of the samples would be within range not 99% of the CI's |

stevo |
expected outcome that is not certain, thus "exactly" is inaccurate. |