In order to investigate whether talking on cell phones is more distracting than listening to car radios while driving, sixty-four student volunteers (from a single college class) were randomly assigned to a cell phone group or a radio group (32 students were assigned to each group). Each student "drove" a machine that simulated driving situations. While "driving" the simulator, a target would flash red at irregular intervals. Participants were instructed to press the "brake" button as soon as possible when they detected a red light. Participant response times were measured as the time between the red light appearing and pushing the brake button. While driving, the radio group listened to a radio broadcast and the cell phone group carried on a conversation on the cell phone with someone in the next room.

The cell phone group had an average response time of 585.2 milliseconds (SD = 89.6), and the control group had an average response time of 533.7 milliseconds (SD = 65.3).

In terms of investigating whether talking on cell phones is more distracting than listening to car radios while driving, which of the following is the correct null hypothesis?

Talking on a cell phone increases your response time compared to listening to the radio.

Talking on a cell phone does not increase your response time compared to listening to the radio.

There is an association between whether one talks on a cell phone or listens to the radio while driving and response time.

There is no association between whether one talks on a cell phone or listens to the radio while driving and response time.