The number of sit-ups that all tenth-grade girls can do in 5 minutes is normally distributed. Beth surveyed 20 of her fellow intramural tennis players, all tenth-grade girls, and determined the mean number of sit-ups they could do. Can she make an inference about the population mean for all tenth-grade girls based on the sample?

Beth surveyed fellow intramural tennis players rather than selecting girls randomly from all tenth-grade girls. This sample may not represent the whole population, since tennis players could differ in fitness or sit-up ability. Therefore, she cannot make a reliable inference about the population mean; the correct choice is “No, because she did not use a simple random sample.”

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