Tuesday, March 26, 2013

ResearchMethods: Experiments: What is an Experiment? (U8-P1) Sp13

Play the first minute or so.

When you think of a person doing science, doing research, doing an experiment, what images pop into your mind?

Has movies and television shaped your view of science and of experiments?  
Hey, I feel a research question coming on.  We could research that.

If it is not the Frankenstein movies that have shaped your image of scientists doing experiments, what movies or television shows have?

An experiment is a research methodology for determining the causal effects of one or more independent variables on a dependent variable, while controlling for all intervening variables.

Experiments are only one of the possible research methodologies you could use to answer your research questions.  Surveys and interviews, for example, are other research methodologies.  There are benefits and drawbacks when considering which research method to use to answer a research question.  What are some benefits that experiments have, but surveys do not?  What is it that experiments can do, that surveys cannot?

What is meant by causal relationship or causal effect?
Or put another way, to be able to say one thing caused another, what would need to be true?

  1. Independent variable comes before the dependent variable.
  2. Independent and dependent variables are meaningfully related.
  3. Changes in DV must be the result of changes in IV (and not anything else)

Correlation vs. Causality: Freakonomics Movie

If you are interested, check out "Correlation and Causality (Khan Academy - YouTube)".

Correlation or Causation? (Some headlines)
Correlation vs. Causation (NYT)

What is experimental control?
The ability to rule out alternative explanations for the results, controlling for all intervening variables.
You want the IV to be the only thing causing an change in the DV.

In real estate it is location, location, location.
In experiments, it is control, control, control.

How can experimental control be enhanced?

Compare experimental control in the lab vs. field study.
  • In lab, can more easily manipulate IV.
  • In lab, can randomly assign participants TR and C groups
  • In lab, can control extraneous variables.
  • In field, max external validity

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