- Dr. Vallerga and Dr. Ligda are interested in the effects of cell-phone use while driving on the
number of driving errors (e.g., running red lights, failing to maintain a safe distance between other cars, slowed reaction time). The researchers tested a sample of 40 individuals in a driving simulator. Participants were randomly assigned to one of two groups of 20 people each. The Cell-phone group talked on the phone (using a hands-free device) and the second group talked with a passenger in the car. The number of driving errors was recorded. The researchers hypothesize that participants in the Cell-phone group would have more driving errors than participants in the Passenger group.