A survey was taken of students at a large university in the fall of 2003; among other things, students were asked to report their weight and their age.
a. Use software to access the student survey data and produce a scatterplot of weights versus ages.
b. Report the correlation r and tell whether the relationship is strong and negative, weak and negative, weak and positive, or strong and positive.
c. It is possible that the relationship seen between weight and age is really due to gender. If male students tended to be older than female students, would the correlation between weight and age be positive or negative?
d. Separate the weights and ages for males and females, and produce correlations separately for males and females.
e. The relationship seems to be a bit stronger for one group-is it males or females?
f. The regression equation for females is approximately Weight = 112 + 1(Age). This suggests that for every additional year, a female student will weigh how many more pounds?
g. The regression equation for males is approximately Weight = 92 + 3.9(Age). Predict the weight of a 20-year-old male.
h. The standard deviation of male weights is 33 pounds. If we use the regression equation to predict a male's weight, given his age, is the typical prediction error less than 33, equal to 33, or greater than 33?