# RESEARCH METHODS 3 Experimental Research EXPERIMENTAL RESEARCH Experiment

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RESEARCH METHODS 3. Experimental Research

EXPERIMENTAL RESEARCH • Experiment: Manipulation of one variable under controlled conditions so that resulting changes in another variable can be observed. • Detection of cause-and-effect relationships • How does X affect Y? • X = Independent Variable • Y = Dependent Variable • Independent variable (IV): variable that is manipulated • Dependent variable (DV): variable that is measured

EXPERIMENTAL RESEARCH • Population: entire group • Sample: subset of the population • Random Sampling or Random Selection: Each member of a population has an equal chance of being selected. • Unbiased; objective • Sampling bias: Occurs when a sample is NOT representative of the population. • If the sample is biased, the results are NOT valid

EXPERIMENTAL RESEARCH • Experimental Group: receives special treatment (IV) • Control Group: does not receive special treatment (IV) • Manipulate IV for one group only • Resulting differences in the two groups must be due to the IV • Random Assignment: assignment of participants to groups by chance • Reduces extraneous variables • Reduces bias

EXPERIMENTAL RESEARCH • Extraneous Variable: Any variables other than the independent variable that may influence the dependent variable in a study. 1. Situational 2. Participant 3. Experimental • Confounding of Variables: When the effects of an extraneous variable are difficult to separate from the effects of the independent variable. • Influences the dependent variable

EXPERIMENTAL RESEARCH • Experimenter Bias: experimenter’s expectation influence outcome • Participant Bias: participant's expectation influence outcome • Placebo Effect: Occurs when a participant’s expectations produce change even though they receive a “fake” treatment. • Hawthorne Effect: The tendency of individuals to perform better simply because of being singled out and made to feel important.

EXPERIMENTAL RESEARCH • Double-blind: BOTH the participants and the experimenters remain unaware of which participants are in the experimental group and control group. • This eliminates both participant bias and experimenter bias • Used for drug trials

EXPERIMENTAL RESEARCH EXPERIMENTAL VARIATIONS • Expose a single group to two different conditions -Reduces extraneous variables • Manipulate more than one independent variable - Allows study of interactions between variables • Measure more than one dependent variable - Obtains a more complete picture of effect of the independent variable

EXPERIMENTAL RESEARCH Description: Manipulation of one variable under controlled conditions so that the resulting changes in another variable can be observed. Advantages • Shows cause and effect relationship!!! • Manipulation of variables • Precise Control • Generalizability Disadvantages • Artificial situations • Costly • Ethical issues