A population of middle school students contains 160 sixth graders, 180 seventh graders, and 140 eighth graders. Nine seventh graders were part of a random sample of the population chosen to participate in a survey. For the sample to accurately represent the population, about how many sixth graders should be chosen?

To represent the population proportionally, the ratio of sixth graders to seventh graders in the sample should match their ratio in the population. There are 160 sixth graders for every 180 seventh graders, so with 9 seventh graders, the number of sixth graders should be 9 × (160 ÷ 180) = 8. The correct choice is 8.

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