POSC300 Lecture Notes - Lecture 9: Spurious Relationship, Internal Validity, External Validity
24 Oct 2018
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A change in one entity brings about a change in another. Two things are both affected by a third factor. Causality is determined by your research design. Two groups; experimental group and control group. Random assignment among individuals to the two groups; no significant difference between groups. Pretest: prior to treatment, everyone is tested on the dependent variable. Post-test: after treatment everyone is tested on the dv. If the experimental response is different from the control group, the iv is the cause. Not interested in individual responses, we want a group response. Allows them to rule out confounds that might influence the. Researchers can control exposure to iv, and therefore control the time-order element of causality. Researcher can control external environment to isolate the effects of the iv. Iv did cause the effect on the dependent variable. Experiments are best at providing internal validity - not guaranteed.
