**Answer:**

The 95% confidence interval for the true difference between the mean birth weights for "zinc" babies versus "placebo" babies is (-515.8566, -192.1434)

**Step-by-step explanation:**

Let be the true difference between the mean birth weights for "zinc" babies versus "placebo" babies. We have the sample sizes babies and babies, the unbiased point estimate for is , i.e., 3072-3426 = -354

The standard error is given by , i.e.,

= 82.5799. Then, the endpoints for a 95% confidence interval for is given by

-354-82.5799 and -354+82.5799, i.e.,

-354-82.5799 and -354+82.5799 where is the 2.5th quantile of the standard normal distribution, i.e., -1.96, so, we have

-354-(1.96)(82.5799) and -354+(1.96)(82.5799), i.e.,

-515.8566 and -192.1434