- CFA Exams
- CFA Level I Exam
- Topic 1. Quantitative Methods
- Learning Module 7. Estimation and Inference
- Subject 2. The Central Limit Theorem and Inference

###
**CFA Practice Question**

A manufacturer of light bulbs claims that the distribution of the light bulb life span has a mean of 60 hours and a standard deviation of 4 hours. The competition decides to check this claim by purchasing 30 light bulbs and testing them to determine their life span. If the manufacturer's claim is true, how will the sampling distribution of the 30 light bulbs compare to the reported population distribution?

A. The sampling distribution will be approximately the same as the population distribution: skewed if the population is skewed, normal if the population is normal.

B. The sampling distribution will have a standard deviation of 4 hours.

C. The sampling distribution will be approximately normal with a mean of 60 hours.

###
**User Contributed Comments**
5

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

xjarl |
Sample will be normally distributed even if sampling from a skewed distribution. |

Profache |
central limit theorem |

farrahkame |
can someone explain this further please? why not A since it wasn't said that the distribution was normal in the first place? |

wahahachan |
The manufacturer NEVER said that the life span of bulbs are normally distributed. Clearly a wrong question. |

ange |
@wahahachan: The population does not have to be normal, but the sample will be. The question is correct. |