The following model is a simplified version of the multiple regression model used by
Biddle and Hamermesh (1990) to study the trade-off between time spent on sleeping and working
and to look at other factors affecting sleep:

Where sleep and totwrk (total work) are measured in minutes per week and educ and age are
measured in years.
A. If adults trade off sleep for work, what is the sign of ?
B. What signs do you think and will have?
Using the data we estimated the equation and obtained (the standard errors in brackets):
Sleep = 3.638.25 - 0.148 totwrk - 11.13 educ + 2.20age
(112.28) (0.017) (5.88) (1.45)
n = 706 R2 = 0.113