IMathAS-libretexts

A medical researcher wanted to estimate μ, the mean weight of newborns born to women over the age of 40.

The researcher chose a random sample of 100 pregnant women who were over 40, followed them through the pregnancy, and found that the mean weight of the 96 newborns was 3,035 grams. From past research, it is assumed that the weight of newborns has a standard deviation of σ = 500. The researcher calculated the 95% confidence interval for μ to be (2935, 3135).

If the researcher wanted to maintain the 95% level of confidence but report a confidence interval with a smaller margin of error, which of the following will achieve that?

Redo the study, but this time with a sample of size 64.
Redo the study, but this time with a sample of size 225.
Redo the study and choose a different sample of size 100.

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