Ex 7.1 Answer

You should read the post ‘Resisting Statistics’ and try exercise 7.1 on your own before looking at the following explanation.

What is the Claim?

The claim appears to be that “living in the US makes you fat”.
However, as a bare claim it clearly is not supported by the premises. Not everyone who lives in the US is fat, and indeed the argument is not about everyone living in the US. So we have to qualify the rather sensationalist journalistic headline to make the claim something more reasonable if the argument is going to stand any weight:

“Living in the US increases the risk of obesity for immigrants.”

This certainly seems to be what the text is trying to argue, but does it do so convincingly?

What kind of an argument is it?

This is an inductive argument based on statistics. Weighing such arguments depends on

i. whether the sample is large enough to be representative, and
ii. whether there are plausible competing explanations for the data.

In this case, the sample (32,000 +) is large enough relative to the domain, and should be a reliable indicator of the general trend. Secondly, there does not appear to be any other obvious explanation that would account for the data. On those grounds, it might be said to be a good inductive argument.

Is it a good argument?

But wait! Notice that there is an exception to the rule: it does not hold for foreign born blacks. The question we must immediately ask is: Why doesn’t it hold for foreign-born blacks? Why are they an exception?

The answer to this could either support or destroy the claim, depending on how it comes out. We might suspect that, given this, at best the argument is incomplete and at worst, it could turn out to be totally false. It all depends on how the anomaly can be explained. That will certainly need further empirical research. In the meantime, critical thinkers need to be circumspect about the qualified claim, and of course reject out of hand the bare “sensationalist” claim made in the opening sentence.

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