13.24 Construction Projects In a study to examine the relationship between the time required to complete a construction project and several pertinent independent variables, an analyst compiled a list of four variables that might be useful in predicting the time to completion. These four variables were size of the contract, x (in $1000 units), number of work- days adversely affected by the weather x2, number of subcontractors involved in the project x4, and a variable x3 that measured the presence (x3 = 1) or absence (x = 0) of a workers' strike during the construction. Fifteen construction projects were randomly chosen, and each of the four variables as well as the time to completion were measured.

An analysis of these data using a first-order model in X1, X2, X3, and x4 produced the following printout. Give a complete analysis of the printout and interpret your results. What can you say about the apparent contribu- tion of x and x2 in predicting y? 

> X1 X2 88 29 60 7 15 80 10 200 X3 X 7 8 60 100 8 1 10 10 50 14 0 5 70 200 12 1 11 15 50 4 0 3 75 500 15 1 12 30 75 5 0 6 45 750 10 0 10 90 1200 20 1 12 7 70 5 0 3 2888 21 80 3 0 6 300 8 50 30 2600 14 110 7 110 8 13 4