- CFA Exams
- CFA Level I Exam
- Study Session 3. Quantitative Methods (2)
- Reading 10. Sampling and Estimation
- Subject 1. Introduction

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**CFA Practice Question**

Samuel Student wanted a random sample of 50 students. He decided to choose the first 50 students entering one of the dining halls at a randomly selected time during the dinner hour.

A. Is his sample random? Why or why not?

B. Is his sample representative? Why or why not?

Correct Answer: Not random; Not representative

His sample is not random. Those who eat elsewhere, i.e., those who live off campus, have no chance of being selected. Thus, not every student has the same chance of being selected as every other; this makes the sample non-random.

There is no way of knowing whether the sample accurately represents or mirrors the population of students. For some purposes it may, for others, maybe not.

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**User Contributed Comments**
3

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

dcfa |
ambigous, how do we assume that not all students were supposed to come to the dining hall |

cleopatraliao |
random sampling=every one has an equal chance of being picked:) |

johntan1979 |
The explanation given is logical... you can't expect EVERY student to go to the dining hall to eat, in reality. Some may be fasting, or eat at other times. Some richer students would dine at posh restaurants, thus making this a biased sample, since not every student is represented equally. |