- CFA Exams
- CFA Level I Exam
- Topic 1. Quantitative Methods
- Learning Module 7. Estimation and Inference
- Subject 1. Sampling Methods

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**CFA Practice Question**

A systematic sampling method should not be used when ______

A. the data are systematically biased.

B. the data are divided into open-ended classes.

C. the data are already arranged in the form of a predetermined pattern.

**Explanation:**If the data are already arranged in the form of a predetermined pattern, using systematic sampling can introduce a systematic pattern in the sample itself, which would lead to erroneous inferences about the entire population.

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**User Contributed Comments**
4

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

ljamieson |
And that is why random sampling should always be used! |

chamad |
What's systematic sampling? |

jpducros |
Good question chamad...apparently systematic sampling would consist in selecting every kth member from a population, where k, the sampling interval (sometimes known as the skip) is calculated as k= N/n where n is the sample size and N is the population size. Ex : From a population of 120 item, you want to sample 8 items. 120/8=15, so every 15th item is chosen, after a random starting point between 1 and 15. If random starting point is 11, then the item selected are 11,26,41,71,86,101 and 116. |

Jurrens |
think of a new deck of cards that hasn't been shuffled yet... |