Critical Thinking & Information Literacy Across the Curriculum

## Statistical Reasoning & Generalizations

Philosophy 115 Assignment 11:

The aim of this assignment is to help students critically evaluate statistical generalizations.

The instructor gives students examples of public opinion polls. Students are then asked several questions about the statistical generalizations that might be made about the poll. Here’s a possible example. More examples could be found from Time Magazine’s Web site at:
http://www.time.com/time/.

Consider the following public opinion poll: Should the U.S. have stricter gun control laws?

1. What statistical generalization might be made from the poll results?
2. Just from the information you have here, do you have any reason to think that this is a good generalization? Do you have any reason for thinking that we would not be justified in accepting this generalization?
3. What additional information would better enable you to evaluate this generalization? (Be specific.)
4. Suppose I tell you that this poll was taken on the Web at the Time Magazine Web site. That is, the poll respondents were those people who visited the magazine’s Web site and answered their question. How does this information affect your assessment of the generalization made? Is the generalization a good one? (NOTE: Giving a full answer to this question will require you to explain what makes a generalization justified, and how, exactly, this poll seems to meet or fail to meet those requirements.)

Students should consider whether the sample size is large enough, whether the sample is well-studied, and whether the sample is biased. This sample is a biased sample. It was not a random sample. The people polled were only those people who a) read Time, and b) have access to the Web. Also, there’s no way of knowing whether the same people voted more than once.

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