Research Designs

Independent measures designs have the problem of participant variability.  What does this mean?

• Participants are not the same as the general population and the results cannot be generalized.

• Participants drop out of the study because of boredom.

• Participants have different levels of skill, so some understand the directions better than others.

• Differences in the traits and past experiences of the participants in each condition may affect the results of the study.

Which of the following is not true of a repeated measures design?

• Fewer participants are needed than for an independent samples design.

• Participants are less likely to show demand characteristics than in an independent samples design.

• Participant variables are controlled.

• Participants are more likely to show order effects - such as improvement of a skill through practice - than in an independent samples design.

A researcher wants to find out if talking on a hands-free mobile phone affects one's driving ability.  Participants were asked to take a driving test in a driving simulator that monitored their mistakes.  In one condition, the participants were asked simply to take the driving test.  In the second condition, the participants were asked to dial up a friend and to have a conversation while taking the driving test.  Half the group did the first condition and half the group did the second condition. Then both groups took a one-hour break before taking the test again - but in the other condition.  What is the best description of the design of this study?

• A longitudinal case study

• A counterbalanced independent samples design

• A counterbalanced repeated measures design

• A counterbalanced matched pairs design

Why would a researcher use a matched-pairs design?

• So that each participant experiences both conditions of an experiment.

• To control for participant variability within a sample.

• To make sure that the order in which the experiment is done does not affect the results.

• To make sure that there are equal numbers of participants in each group

Which of the following is not an order effect?

• Fatigue

• Social desirability effect:  participants give responses that are "socially acceptable."

• Boredom with the study

• Practice effect - participants get better at the skill being studied, just because they keep doing it during the experiment.