Video: Selecting Samples

Jennifer is doing a research project on whether or not students in her school eat healthy food. She decides to interview her friends who do gymnastics with her. Is her sample biased?

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Video Transcript

Jennifer is doing a research project on whether or not students in her school eat healthy food. She decides to interview her friends who do gymnastics with her. Is her sample biased?

In order to work out if any sample is biased, we need to ask ourselves one question. The question is this: does every member of the population have an equal chance of being selected? In this question, the students in Jennifer’s school are the population. She’s researching whether they eat healthy food or not. In Jennifer’s sample, she’s only selecting friends from gymnastics. This means that any students in the school who do not do gymnastics cannot be selected.

The answer to the question “Does every member of the population have an equal chance of being selected?” is therefore no. If this is the case, we know that the sample is biased or unfair. The correct overall answer is, therefore, yes, Jennifer’s sample is biased. This is because the only students that can be selected in her sample are those that do gymnastics. It is also quite possible — although not certain — that many of the students who do gymnastics eat healthy food. This means that the sample that she has chosen could skew the results of her research project. They could potentially give a more positive outlook on those students who eat healthy food.

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