POL222H1 Lecture Notes - Lecture 3: Negative Relationship, Spurious Relationship, Confounding
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Two primary, potential obstacles when we empirically examine the causal relationships. Even when we find a systematic relationship between x and y we cannot tell whether x causes y or y causes x or both. X causes y, but what if there are other variable(s) (z) that causes. If there is a relationship between x (independent) and z, z is called a confounding variable. If z only has an influence on y (dependent), it is not confounding. More educated, know more about politics, have a stronger interest in politics. Confounding variable that has a relationship with both x and y --> Original relationship between x and y is gone, now is a spurious relationship. Relationship is a result of confounding variable that links the two variables. Elementary school teacher that is trying to find out what would improve student"s academic achievement. Data demonstrates that the taller students perform better (positive relationship)