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July 28, 2014

July 28, 2014

Posted by **Anonymous** on Monday, October 31, 2011 at 4:44pm.

- statistics -
**Anonymous**, Monday, October 31, 2011 at 4:46pmA researcher is investigating whether, on average, 3rd grade males have significantly different creativity scores than 3rd grade females. She samples students from a large school district where she works. What is the independent variable? A non-directional alternative for the study would be? What type of research design would this be?

- statistics -
**PsyDAG**, Monday, October 31, 2011 at 6:30pmGender is the independent variable.

An**independent variable**is the potential stimulus or cause, usually directly manipulated by the experimenter, so it could also be called a manipulative variable.

A**dependent variable**is the response or measure of results.

Ho: girls' scores = boys' scores

Ha: girls' scores ≠ boys' scores

For research design, this might be helpful:

1.**Single blind**gives the control group a**placebo**— a substance that is inert, it has no physical effect. Subjects don't know if they are in experimental or control group to reduce placebo effect, a change in behavior solely due to believing that you are getting the independent variable.

2.**Double blind**keeps both subjects and experimenter ignorant of group setup. Distribution of the independent variable and placebo are controlled by third party. This controls for experimenter bias and**self-fulfilling prophecy**, which means that experimenters with particular expectations are likely to consciously or unconsciously to bias the experiment and influence it to conform to their expectations.

As an example, suppose you want to find out if fluorides reduce dental cavities. You would find two groups, trying to control the extraneous variables. Extraneous variables are found by surveying previous research in the area. In this case, you would match the groups in terms of previous history of cavities, diet and dental hygiene habits including how and how often they brush their teeth.

The experimental group would get toothpaste with the independent variable, the fluoride, while the control group would not have the fluoride in their toothpaste. The toothpaste without the fluoride would be the placebo.

The dependent variable would be the number of cavities after participating in the experiment for a time. The dependent variable indicates the results, but it is*not*the results. At the end of the experiment, both groups could have no change in cavities or one of the groups could have a greater reduction in cavities. (Of course, if the fluoride increased cavities, you wouldn't want to use it.) All of these varied results would be indicated in terms of the dependent variable.

If only the subjects do not know who is getting the fluoride, it is a single blind experiment. If both the subjects and experimenter do not know, it is a double blind.

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