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Experiments

Experiments. Unit 2 – Mod 5. Experiment. Carefully controlled method of investigation used to establish a cause-and-effect relationship Experimenter purposely manipulates and controls selected variables. Variables. Independent Variable (IV)

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Experiments

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  1. Experiments Unit 2 – Mod 5

  2. Experiment • Carefully controlled method of investigation used to establish a cause-and-effect relationship • Experimenter purposely manipulates and controls selected variables

  3. Variables • Independent Variable (IV) • Factor that is manipulated or controlled by the experimenter. • Dependent Variable (DV) • Factor that is measured by the experimenter • Affected by IV

  4. Let’s Practice… • An experimenter wants to determine if playing violent video games increases the frequency of aggressive behavior in children. • An experimenter wants to determine the relationship between rehearsal/repetition of a list of definitions of difficult SAT vocabulary words and later recall of these definitions.

  5. Operational Definition • Precise description of how the variable in a study will be manipulated and measured.

  6. Experiment • Experimental Group • Participants who get the treatment (independent variable) • Control Group • Participants who are exposed to all experimental conditions except the independent variable.

  7. Confounding Variables • Differences between the experimental group and the control groups other than the IV • Have an unwanted influence on the outcome of an experiment • Example… • In a study measuring the impact of playing violent video games on the frequency of aggression in children • Confounding variables • Income level of kid’s parents • Incidence of child abuse

  8. Experimental Controls • Purpose • Used to ensure that all groups in the experiment are treated exactly the same, except for the IV • Problems • Experimenter bias • Sample bias – research participants are not representative

  9. Solutions to stop bias • Random assignment • Minimizes pre-existing differences between groups • Placebo • An inactive substance or fake treatment often used as a control technique in drug research

  10. Solutions • Single-blind study • Procedure in which the subjects do not know whether they are in the experiment or control group • Double-blind study • Procedure in which neither the researcher nor the participant knows which group

  11. Advantages • Identifies cause-and-effect • Distinguish between real and placebo effects • Control bias with double-blind • Allows for replication

  12. Disadvantages • Artificial lab conditions that do not correspond to real-life situations • Can be compromised by confounding variables • Susceptible to researcher and participant biases • Raises ethical questions when subjects are deceived

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