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a typical experiment

a typical experiment. prototype of a controlled laboratory investigation. In the most typical experiment. Subjects are randomly assigned to a “treatment” or “control” group. The treatment group is exposed to the experimental stimulus.

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a typical experiment

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  1. a typical experiment prototype of a controlled laboratory investigation

  2. In the most typical experiment • Subjects are randomly assigned to a “treatment” or “control” group. • The treatment group is exposed to the experimental stimulus. • The control group is not exposed to the experimental stimulus • The researcher measures any resulting differences between the treatment and control group

  3. Example 1: treatment group versus control group • RQ: Does caffeine consumption increase physical stamina? • Independent variable: caffeine consumption versus no caffeine consumption • Dependent variable: physical stamina as measured by the total distance jogged on a treadmill in 1 hour.

  4. Random assignment • Random assignment produces equivalent groups for comparison purposes • 200 volunteers are randomly assigned to a treatment group or control group N = 200 treatment group = 100 control group = 100

  5. treatment group Consumes 12 oz. (500 milligrams) of coffee just before jogging on a treadmill control group Consumes 12 oz. Of decaffeinated coffee just before jogging on a treadmill Operationalization of the independent variable

  6. Measurement of the dependent variable • The total distance of each jogger is measured by the treadmill’s counter to the nearest 1/10 mile. There is a 1 hr. time limit. Two observers watch to ensure the joggers are jogging (8-12 minute pace), not walking, until they stop. • The average distance of the joggers in the treatment group is compared with the average distance of joggers in the control group.

  7. Example 2: comparison groups • RQ: Do dog owners report greater relationship satisfaction than cat owners? • Independent variable: pet ownership, e.g., dogs owners versus cat owners • Dependent variable: relationship satisfaction, as measured by the “Dyadic Adjustment Scale.”

  8. Non-random assignment • Some experiments rely on “intact” or “self-selected” groups • People already own their pets. They can’t be randomly assigned to own one pet or another

  9. 91 dog owners are selected using a “mall intercept” technique The dog owners do not own a cat or any other pets. 103 cat owners are selected using a “mall intercept” technique The cat owners do not own a dog or any other pets. Operationalization of the independent variable

  10. Measurement of the dependent variable • All of the respondents are asked to complete the “Dyadic Adjustment Scale” • a paper-pencil survey that asks respondents to rate the quality of their relationship with a significant other. • The average ratings of the dog owners are then compared with the average ratings of the cat owners to see if there is a significant difference.

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