The article “Models for Assessing Hoisting Times of Tower Cranes” (A. Leung and C. Tam, Journal of Construction Engineering and Management, 1999: 385–391) presents a model constructed by a step wise regression procedure to predict the time needed for a tower crane hoisting operation. Twenty variables were considered, and the step wise procedure chose a nine-variable model. The adjusted R² for the selected model was 0.73. True or false:

a. The value 0.73 is a reliable measure of the goodness of fit of the selected model.

b. The value 0.73 may exaggerate the goodness of fit of the model.

c. A step wise regression procedure selects only variables that are of some use in predicting the value of the dependent variable.

d. It is possible for a variable that is of no use in predicting the value of a dependent variable to be part of a model selected by a step wise regression procedure.