Find the confidence interval specified:
a) A random sample of 88 light bulbs had a mean life x = 497 hrs. Assume the Standard d = 27 hrs. Construct a 90% confidence interval for the mean life, u, of all light bulbs of this type.
b) A Lab tested 77 chicken eggs and found that the mean amount of cholesterol was 199 milligrams. Assume the SD=16.1 mill. Construct a 95% confidence interval for the true mena of cholesteterol content, u, of all such eggs.