Introduction to Probability and Statistics for Engineers and Scientists

436 Chapter 9: Regression

(a) Estimate the regression parametersαandβ.

(b) What is the qualitative relationship between years of service and job

satisfaction? That is, what appears to happen to job satisfaction as service

increases?

(c) Compare your answer to part (b) with the answer you obtained in part (b) of

Problem 54.

(d) What conclusion, if any, can you draw from your answer in part (c)?

56.For the logistics regression model, find the valuexsuch thatp(x)=.5

57.A study of 64 prematurely born infants was interested in the relation between

the gestational age (in weeks) of the infant at birth and whether the infant was

breast-feeding at the time of release from the birthing hospital. The following data

resulted:

Gestational Age Frequency Number Breast-Feeding

28 6 2

29 5 2

30 9 7

31 9 7

32 20 16

33 15 14

In the preceding, the frequency column refers to the number of babies born after

the specified gestational number of weeks.

(a) Explain how the relationship between gestational age and whether the infant

was breast-feeding can be analyzed via a logistics regression model.

(b) Use appropriate software to estimate the parameters for this model.

(c) Estimate the probability that a newborn with a gestational age of 29 weeks

will be breast-feeding.

58.Twelve first-time heart attack victims were given a test that measures internal

anger. The following data relates their scores and whether they had a second heart

attack within 5 years.

Anger Score Second Heart Attack

80 yes

77 yes

70 no

68 yes

64 no

(continued)