Experimental Designs and Balancing

1. identify whether the experiment is an independent groups experiment or a repeated measures experiment;
2. identify what potential confounding should be balanced in the experiment, individual differences or practice effects; and
3. identify which control technique should be used for balancing, random assignment or counterbalance order of conditions.

1		A researcher has 20 participants rate five inkblots for their "sensuality." Assume that the researcher has a reliable and valid measure of sensuality. Each participant rates each inkblot one time. Design Potential Confounding Control Technique a. independent groups a. individual differences a. random assignment b. repeated measures b. practice effects b. counterbalance order
2		An investigator tests participants’ ability to estimate time. She presents auditory tones for varying lengths of time and after presenting each tone she asks participants to estimate how long (in seconds) the tone was presented. She presents six different tones lasting 14, 21, 28, 35, 42, and 49 seconds. Twelve participants are available for testing. The investigator presents each of the six intervals four times to each participant. Design Potential Confounding Control Technique a. independent groups a. individual differences a. random assignment b. repeated measures b. practice effects b. counterbalance order
3		A psychologist researching child abuse develops a questionnaire to help identify some of the antecedents of this problem. However, he also wishes to test a hypothesis that the ordering of certain critical questions will influence how participants respond on the questionnaire. He prepares two different forms of the questionnaire based on his analysis of the questions and of the possible effects that the order in which these questions appear might have on respondents' answers. The forms differ only in terms of the order in which certain critical questions are presented. Participants are randomly assigned to answer questions on one of the two forms. Design Potential Confounding Control Technique a. independent groups a. individual differences a. random assignment b. repeated measures b. practice effects b. counterbalance order
4		A developmental psychologist tests children's reactions to four different "cereal creatures," – creatures used by the cereal company to advertise their cereals (e.g., Tony the Tiger, Fred Flintstone, et al.). She decides to test 6th graders at a local elementary school. Each child is asked to complete a brief response sheet about each of four cereal creatures. A total of 24 sixth-graders are available for testing. Design Potential Confounding Control Technique a. independent groups a. individual differences a. random assignment b. repeated measures b. practice effects b. counterbalance order
5		A researcher has devised a method to help stutterers. He wants to test the method against an alternative method. Eight stutterers volunteer for the experiment. The researcher decides to ask each stutterer to read a passage aloud to the group using both methods. In fact, he designs the experiment so that the participants read an experimental passage two times with each method. Design Potential Confounding Control Technique a. independent groups a. individual differences a. random assignment b. repeated measures b. practice effects b. counterbalance order
6		In an experiment on interpersonal harm, participants read a hypothetical scenario in which a student loans a computer disk to a friend, who then returns the disk with a flaw on it. The student has trouble retrieving a file with an important paper that needs to be turned in that day. Two versions of the scenario are used; participants read only one version. In one version, the student is able to retrieve the file with the help of an expert at the computer lab. In the second version, the student is unable to retrieve the file. The researcher asks participants whether they would forgive their friend. Design Potential Confounding Control Technique a. independent groups a. individual differences a. random assignment b. repeated measures b. practice effects b. counterbalance order