Psychology-One-Way Experimental Designs

Psychology-One-Way Experimental Designs

The independent and dependent variable and the number of levels in the independent variable

The dependent variable is the time it takes the participants to fall asleep. The independent variable is the pill, which has two effects: feeling sleepy and staying alert for longer hours. The two levels of independent variables are the tendency to make participants “fall asleep” and the second level is “keeping them alert and awake.”

The research design (between-participants or a within-participants)

The research design employed is a between-participants research design since the two groups of participants are tested in similar conditions (Stangor, 2015). The two groups were randomly assigned to the two levels of the independent variable, where they were required to respond to the behaviors under the influence of the placebo. A within-participants study would apply if the two groups of participants were tested in both conditions. The participants can be divided into two groups of 25 participants each.

Presuming a third condition was added to the study and the participants were not given any information about the effects of the (placebo) pill and supposing an analysis of variance (ANOVA) was conducted, the interpretation of F as being significant is

ANOVA is applied to test the difference in population means for more than two populations. The test is applied to test whether the three conditions come from populations with the same mean. In other words, the F-value in ANOVA helps the researcher to answer the question of “Is there any variance between the populations significantly different?” (Glen, 2020). For a significant F value, the test indicates that the F statistic is larger than the f-critical value, which denotes that there exist differences between the population means for the three groups (Stangor, 2015). This implies that the mean time it took the three groups (fall asleep, stay awake and alert, and no information) to fall asleep is different. The result also indicates that at least one condition is different from others. We reject the null hypothesis when the critical f-critical is larger than the F Value. However, the p-value should also be considered to determine whether the results are significant.

References

Glen, S. (2020). “F Statistic / F Value: Simple Definition and Interpretation” From StatisticsHowTo.com: Elementary Statistics for the rest of us! https://www.statisticshowto.com/probability-and-statistics/f-statistic-value-test/

Stangor, C. (2015). Research methods for the behavioral sciences (5th ed.). Stamford, CT: Cengage Learning.

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Assignment: One-Way Experimental Designs
Correlational research, which you explored in this week’s Discussion, is useful in identifying relations between two variables but does not make assumptions regarding cause and effect among the variables because researchers did not control for outside factors. To demonstrate possible causal relations among variables, researchers will need to manipulate variables in an experimental research design.

The variable that the researcher manipulates in an experimental research design is termed the independent variable. As a researcher, one important determination you need to make is the number of independent variables involved in the study. If you manipulate one independent variable, the study would be termed a one-way experimental design.

Researchers also need to determine dependent variables. In an experimental design, the dependent variable is the measure of the effect of the independent variable. If the dependent measure reveals an effect made by an independent variable, a researcher may be able to determine cause.

Psychology-One-Way Experimental Designs

Consider a study that hypothesizes that 8-year-olds who play educational computer games score higher on intelligence tests than those who do not play educational computer games. Consider how many aspects you would need to address if you were conducting the study. First, you would need to understand that the independent variable is the game-playing, whereas the dependent variable is the scores on the intelligence test.

Next, you would need to determine the levels of the independent variable. In this scenario, suppose there are three levels of play: no play, some play (4 hours a week), and frequent play (8 or more hours a week).

Additionally, you would need to determine whether the study is a between-participants design or a within-participants design (also known as a repeated-measures design). A between-participants design uses different groups for each level. A within-participants design uses the same group, and that one group repeats the experiment for each level.

In this Assignment you apply key concepts related to experimental design to a research study and analyze and interpret the outcome.

To prepare:

Read the assigned pages from Chapter 10 in your course text.
Read the following study scenario:
Researchers are interested in the effectiveness of a particular treatment for insomnia. They contacted 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.
Note: Support the responses within your Assignment with evidence from the assigned Learning Resources. Provide a reference list for resources you used for this Assignment.

Resources
Stangor, C. (2015). Research methods for the behavioral sciences (5th ed.). Stamford, CT: Cengage Learning.

Chapter 9, “Correlational Research Designs”
Chapter 10, “Experimental Research: One-Way Designs”