Refer to Exercise 16.139. The gender of the student was recorded where 1 = male and 0 = female.

a. Does the inclusion of gender improve the model?

b. Predict with 95% confidence the height of a female whose index finger is 6.5 cm long.

c. Predict with 95% confidence the height of a male whose index finger is 6.5 cm long.

d. Is this model likely to be useful? Explain.

In exercise 16.139

A computer dating service typically asks for various pieces of information such as height, weight, income, and so on. One such service requested the length of index fingers. The only plausible reason for this request is to act as a proxy on height. Women have often complained that men lie about their heights. If there is a strong relationship between heights and index fingers, the information can be used to “correct” false claims about heights. To test the relationship between the two variables researchers gathered the heights and lengths of index fingers (in centimeters) of 121 students.