91Ó°ÊÓ

Cell Phones and Driving. Does talking on a hands-free cell phone distract drivers? Undergraduate students "drove" in a high-fidelity driving simulator equipped with a hands-free cell phone. The car ahead brakes. How quickly does the subject react? The reaction times will be compared for subjects "driving" with and without using the cell phone. There are 40 student subjects available. 18 (a) What are the response and the explanatory variables? (b) Describe the design of a completely randomized experiment to leam the effect of talking on a hands-free cell phone on reaction time. (c) In a matched pairs design, all subjects drive both with and without using the cell phone. The two drives are on separate days to reduce carryover effects. One of the experimenters wants to assign the order of the two treatments at random: 20 subjects are chosen to drive first with the phone, and the remaining 20 drive first without the phone. The second experimenter argues it would be better to have everyone drive without the phone on the first day and with the phone on the second day so that all subjects are treated alike. Which experimenter do you agree with? Explain why. (d) Suppose there are large differences in the reaction times of the subjects. Would the matched pairs experiment be a better choice than the completely randomized experiment in this case? Explain briefly.

Step by step solution

01

Identify the Variables

The response variable is the variable of interest that measures the outcome of the study. In this experiment, the response variable is the reaction time of the drivers. The explanatory variable is the one that is manipulated to observe its effect on the response variable. In this case, the explanatory variable is whether the person is talking on a hands-free cell phone or not.

02

Design a Completely Randomized Experiment

To design a completely randomized experiment, we would first randomly assign the 40 student subjects into two groups. One group drives with the hands-free cell phone and the other drives without it. The reaction times are then recorded for each group, and the average reaction times are compared to determine the effect of talking on a hands-free cell phone.

03

Analyze Matched Pairs Design Argument

In a matched pairs design, all subjects experience both treatment conditions. The first experimenter suggests randomizing the order, splitting 20 to drive first with the phone and 20 without. The second suggests a fixed order for all. Randomizing helps balance unknown factors possibly affecting reaction time, while a fixed order eliminates variability from day-to-day conditions. Agreeing with the first experimenter brings the advantage of mitigating order effects (bias from practice), making the experimental data more robust against biases.

04

Discuss Choice of Experiment Type for Large Differences

If there are large inherent differences in reaction times among subjects, a matched pairs experiment is advantageous. This is because it ensures each subject serves as their own control, which reduces the variability in the response due to individual differences and allows for more sensitive detection of the effect of the cell phone usage.

Unlock Step-by-Step Solutions & Ace Your Exams!

• Full Textbook Solutions

  Get detailed explanations and key concepts

• Unlimited Al creation

  Al flashcards, explanations, exams and more...

• Ads-free access

  To over 500 millions flashcards

• Money-back guarantee

  We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Response Variable

In any scientific study, identifying the response variable is crucial because it represents what is being measured or observed. In the cell phone and driving study, the response variable is the reaction time of the drivers. Reaction time indicates how quickly a driver reacts to a situation, such as the car ahead braking. Understanding this variable helps researchers decide how distractions, like talking on a hands-free cell phone, impact driving performance.

The response variable must be clearly defined to ensure accurate data collection and meaningful analysis. By consistently measuring reaction time across all participants, researchers can see how it varies depending on different conditions, such as using or not using hands-free technology.

Explanatory Variable

The explanatory variable is what researchers manipulate to determine its effects on another variable, often the response variable. In this experiment, the explanatory variable is whether the driver is using a hands-free cell phone while driving.

• If drivers are talking on the phone, this condition represents one state of the explanatory variable.
• If drivers are not using the phone, this condition represents the other state.

By observing changes in the response variable (reaction time), researchers assess how much influence the explanatory variable (phone usage) has. Clearly distinguishing between these variables helps ensure the validity of the experimental results by directly linking cause (using the phone) to effect (reaction times).

Randomized Experiment

Randomized experiments are vital for reducing biases and ensuring that the results are due to the treatment effect rather than extraneous variables. Here, subjects are randomly assigned to test groups (with and without cell phone usage) to examine its impact on reaction time.
This randomness helps to distribute any unknown confounding factors evenly between the groups, allowing an unbiased comparison of the groups' reaction times.

• Increasing randomness improves the reliability of the findings.
• Statistical methods can be applied to assess the differences observed in reaction times.

Randomization is a critical component in scientific research, providing a fair test of the hypothesis about hands-free phone usage and driver distraction.

Matched Pairs Design

The matched pairs design is an effective approach when studying the effect of variables within the same subjects over different conditions. Each participant in the study experiences both conditions (with and without phone usage), effectively serving as their own control.
This design aims to minimize individual differences by comparing each subject to himself or herself.

• It helps eliminate differences inherent to the subject, such as baseline reaction times.
• Matched pairs design is more powerful in detecting small but significant differences due to its control over subject variability.

When handling large differences in individual reaction times, this method is preferred because it highlights the true impact of hands-free cell phone usage on each driver, making findings more accurate and relevant.