- Read the following study scenario:
Researchers are interested in the effectiveness of a particular treatment for insomnia. They contact 50 insomnia sufferers who responded to a newspaper advertisement to participate in the study. Each participant is given a pill with instructions to take it before going to sleep that night. The pill actually contains milk powder (a placebo). The participants are randomly assigned to receive one of two sets of instructions about the pill. One half of the participants are told that the pill will make them feel “sleepy,” and the other half are told that the pill will make them feel “awake and alert.” The next day the participants return to the lab and are asked to indicate how long it took them to fall asleep after taking the pill. The individuals who were told that the pill would make them feel sleepy reported that they fell asleep faster than the participants who were told the pill would make them feel alert.
Think about the concepts you read about this week about one-way experimental designs and analysis of variance (ANOVA), and how they apply to the above study.
The Assignment (1–2 pages):
With the study scenario in mind, complete the following:
- Identify the independent variable and dependent variable. Indicate the number of levels in the independent variable and describe each level.
- Indicate whether the research used a between-participants or a within-participants research design and how you determined this to be the case.
- Presume a third condition was added to the study. In this condition, the participants are not given any information about the effects of the (placebo) pill. Next, suppose an analysis of variance (ANOVA) was conducted. Briefly interpret, in your own words, what it would mean if the F was significant as applied to this study.