Also state what Critical Value is please

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 243 babies in the zinc group had a mean birth weight of 3197 grams. A sample of 268 babies in the placebo group had a mean birth weight of 3395 grams. Assume that the population standard deviation for the zinc group is 841 grams, while the population standard deviation for the placebo group is 637 grams. Determine the 95 % confidence interval for the true difference between the mean birth weights for "zinc" babies versus "placebo" babies. Step 2 of 2: Construct the 95 % confidence interval. Round your answers to the nearest whole number. Answer(How to Enter) 2 Points Keypad Keyboard Shortcuts Lower endpoint: Upper endpoint