5. A recent study of mail survey response rate patterns of the elderly found a prediction equa- tion relating X = age and Y = percentage of subjects responding of = 90.2-.6X, for ages between about 60 and 90 (D. Kaldenberg et al. Public Opinion Quarterly, Vol 58, 1994, p. 68).

a) Interpict the slope.

b) Find the predicted response rate for a (i) 60 year old, (ii) 90 year old.

c) Find the difference in predicted response rates for two age groups that are ten years apart.