A group of scientists used human subjects (16 young adults) to genederate footprints in sand. The response variable of interest was heel depth (y) of the footrprint (in inches). Six potential explanatory varaibles were investigated: foot mass (grams), leg length (meters), foot type (flat or arched), velocity (meters per second), pressure (newtons per cm2), and impulse (newton-seconds per cm). A forward selection stepwise regression procedure is run to choose an appropriate model. The model using pressure and leg length as the only predictors in the model. Suppose that the initial model using one-variable is chosen by fitting each of the explanatory varaiables to a simple linear regression model for predicting heel depth. At minimum, how many t-tests on individual slope terms must have been conducted to arrive at the final model using pressure and leg length