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handout_2_6 - 2.6 The Question of Causation Often the goal...

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2.6 The Question of Causation Often the goal in a study is to establish that changes in the explanatory variable cause changes in the response variable. What constitutes good evidence of causation? What different types of links between x and y can explain an observed association between x and y? dotted line→ association between x and y unbroken line→ cause-and-effect link between x and y Causation - “x causes y” EX #1 x= mother’s body mass index y= daughter’s body mass index A study of young girls measured their body mass index (BMI- a measure of weight relative to height) for both the girls and their mothers. The study also measured hours of TV, minutes of physical activity, and intake of several kinds of food. The strongest correlation (r= 0.506) was between the BMI of daughters and the BMI of their mothers. Body type is in part determined by heredity. There is therefore a direct causal link between the BMI of mothers and daughters. •Even when direct causation is present, it is rarely a complete explanation of an
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This note was uploaded on 05/25/2010 for the course PAM 2100 taught by Professor Abdus,s. during the Spring '08 term at Cornell.

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handout_2_6 - 2.6 The Question of Causation Often the goal...

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