Newborn jaundice is when a baby has a high level of bilirubin in the blood. Bilirubin is a yellow substance produced by the normal breakdown of red blood cells. We would like to estimate the mean serum bilirubin level of 4-day old infants using a sample of 150 infants. The observed sample mean for these 150 infants is 5.96 mg/100 cc. Since the sample size is large, we construct a 95% confidence interval for the mean based on z, and we obtain the interval [5.3279; 6.5921].

(a) Compute the estimated standard error of the mean.

(b) Give the value of the sample standard deviation for these 150 infants.

(c) Without computing the interval, would you expect a 97% confidence interval for the mean to be larger, smaller or of the same length compared to the above 95% confidence interval. (Why?)

(d) Give a 97% confidence interval for the mean serum bilirubin level of 4-day old infants.