Researchers developed a safety performance function (SPF), which estimates the probability of occurrence of a crash for a given segment of roadway. Using data on over 100 segments of roadway, they fit the model E(y)=0+1x1+2x2, where of crashes per three years, length (miles), and annual daily traffic (number of vehicles) = AADT.

Interstate Highways

Variable	Parameter Estimate	Standard Error	t-value
Intercept	1.87602	0.59586	3.74
Length (x1)	0.10378	0.03675	3.35
AADT (x2)	0.00014	0.00004	6.54

Non-Interstate Highways

Variable	Parameter Estimate	Standard Error	t-value
Intercept	1.23827	0.25382	3.81982
Length (x1)	0.56732	0.02435	3.08063
AADT (x2)	0.00051	0.00013	6.12662

c. Refer to (.87602 + 0.10378x1 + 0.00014x2) Find a 98% confidence interval for 1.

( , )

d. Refer to (.87602 + 0.10378x1 + 0.00014x2) Find a 98% confidence interval for 2.

( , )

e. Give the least squares prediction equation for the interstate non-highway model.

Y= ( ) + ( )x1 + ( )x2

*Find a 98% confidence interval for 1.

( , )

*Find a 98% confidence interval for 2.

( , )