738 Husbands and wives Part III Exercise 737 presents a scat

7.38 Husbands and wives, Part III. Exercise 7.37 presents a scatterplot displaying the
relationship between husbands\' and wives\' ages in a random sample of 170 married couples in
Britain, where both partners\' ages are below 65 years. Given below is summary output of the least
squares t for predicting wife\'s age from husband\'s age.

(e) You meet a married man from Britain who is 55 years old. What would you predict his wife\'s age to be? How reliable is this prediction?
(f) You meet another married man from Britain who is 85 years old. Would it be wise to use the same linear model to predict his wife\'s age? Explain.

60 Estimate Std. Error t value Pr(lt D 40 (Intercept) age_husband 1.5740 0.9112 1.1501 0.0259 1.37 35.25 0.1730 0.0000 20 20 40 60 Husband\'s age (in years)

Solution

a)

The regression line is

wife age = 1.574+0.9112 * husband age

when husband age =55,

wife age = 1.574+0.9112 * 55

= 51.69

It is reliable because the husband age is within the range of x values and the regression is significant.

b).

It is not wise to use the same linear model to predict his wife\'s age, because the husband age is not within the range of x values.