The data set lowbwt contains information recorded for a sample of 100 very low birth weight infants — those weighing less than 1500 grams — born in two teaching hospitals in Boston, Massachusetts [81]. Measurements of systolic blood pressure are saved under the variable name sbp. The dichotomous random variable sex designates the sex of each child, with I representing a male and 0 a female.

(a) What type of numerical data is systolic blood pressure?

(b) What type of numerical data is sex?

(c) Construct a pair of box plots for the systolic blood pressure measurements — one for boys and one for girls. Compare the two distributions of values.

(d) Compute the mean and standard deviation of systolic blood pressure for males and for females. Which group has the larger mean? The larger standard deviation?