Question

A scientist studying babies born prematurely would like to obtain an estimate for the mean birth weight, μ, of babies born during the 24th week of the gestation period. She plans to select a random sample of birth weights of such babies and use the mean of the sample to estimate μ. Assuming that the population of birth weights of babies born during the 24th week has a standard deviation of 2.7 pounds, what is the minimum sample size needed for the scientist to be 99% confiden that her estimate is within 0.6 pounds of ? Carry your intermediate computations to at least three decimal places. Write your answer as a whole number (and make sure that it is the minimum whole number that satisfies the requirements). (If necessary, consult a list of formulas-)

Answer 1

So, the minimum sample size needed is 134 babies born during the 24th week of the gestation period.

To find the minimum sample size needed for the scientist to be 99% confident that her estimate is within 0.6 pounds of the true mean birth weight (μ), we can use the formula:
n = (Z × σ / E)²
where n is the sample size, Z is the Z-score corresponding to the desired confidence level (99%), σ is the standard deviation of the population (2.7 pounds), and E is the margin of error (0.6 pounds).
For a 99% confidence level, the Z-score is 2.576. Now, we can plug the values into the formula:
n = (2.576 × 2.7 / 0.6)²
n = (6.9456 / 0.6)²
n = 11.576²
n ≈ 133.76
Since the sample size should be a whole number, we need to round up to the nearest whole number to ensure the minimum requirement is met:
n ≈ 134