6.3.3 As part of a study of the development of the thymus gland, researchers weighed the glands of five chick embryos after 14 days of incubation. The thymus weights (mg) were as follows12: 29.6 21.5 28.0 34.6 44.9 For these data, the mean is 31.7 and the standard devia- tion is 8.7. (a) Calculate the standard error of the mean. (b) Construct a 90% confidence interval for the population mean.