Each of the following conclusions is based on a relationship between X and Y tha

Question

Each of the following conclusions is based on a relationship between X and Y that is completely spurious. For each one: (i) Think up a plausible variable, Z, that defines a compositional difference across the values of X. (ii) Describe how Z creates the relationship between X and Y.
Example: Red cars (X) are more likely to be involved in accidents (Y) than are nonred cars. Conclusion: If red cars are banned, the accident rate will decline. (i) Driver age (Z). (ii) Drivers of red cars are younger than drivers of nonred cars. Younger people have higher accident rates (Y) than do older people. As car color (X) varies, driver age (Z) varies, which causes accident rates (Y) to change.

A.   Students who smoke (X) earn lower grades (Y) than students who do not smoke. Conclusion: Smoking causes poor grades.

B.   Expectant mothers who drink bottled water (X) have healthier babies (Y) than do expectant mothers who do not drink bottled water. Conclusion: Drinking bottled water causes healthier babies to be born.

C.   Tea drinkers (X) are more likely to be Democrats (Y) than are non–tea drinkers. Conclusion: Tea drinking causes people to become Democrats.

Explanation / Answer

A. i) The variable is Z: Concentration, ii) students who smoke are supposedly more distracted, and less concentrated than students who do not smoke. Therefore, students who smoke and less concentrated tend to score low grades (Y). Thus, as X varies, Z varies, and so the Y.

B) i) The variable is Z: Dissolved minerals, ii) expectant mothers who drink bottled water, are supposedly exposed to more dissoled materials, which is helpful for in fulfilling a certain percent of nutrient requirement, giving birth to healthier babies Y. Thus, as X varies, Z varies, and so the Y.

C) i) The variable is Z: Age, ii) Usually tea drinkers are of older age and comprised of lighter stance on political issues, so as X varies, Z varies, and so the Y.

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