Question

The birth weights for two groups of babies were compared in a study. In one group the mothers took a zinc supplement during pregnancy. In another group, the mothers took a placebo. A sample of 259 babies in the zinc group had a mean birth weight of 3428 grams. A sample of 218 babies in the placebo group had a mean birth weight of 3022 grams. Assume that the population standard deviation for the zinc group is 568 grams, while the population standard deviation for the placebo group is 563 grams. Determine the 98% confidence interval for the true difference between the mean birth weights for "zinc" babies versus "placebo" babies.

Step 1 of 3:

Find the point estimate for the true difference between the population means.

Step 2 of 3:

Calculate the margin of error of a confidence interval for the difference between the two population means. Round your answer to six decimal places.

Step 3 of 3:

Construct the 98% confidence interval. Round your answers to the nearest whole number.

Answer 1

We have and

1. point estimate for the true difference between the population means =

2. Margin of Error =

For 98% confidence,

z-value corresponding to 98% confidence,

Margin of error =

3. confidence interval: