STATISTICS IN SUMMARY

Chapter Specifics

image In reasoning from data to a conclusion, we start with the data. In statistics, data are ultimately represented by numbers. The planning of the production of data through a sample or experiment does not by itself produce these numbers. The extent to which these numbers represent the characteristics we wish to study affects the quality and relevance of our conclusions. When you work with data or read about a statistical study, ask exactly how the variables are defined and whether they leave out some things you want to know. This chapter presents several ideas to think about in assessing the variables measured and hence the conclusions based on these measurements.

CASE STUDY EVALUATED The Case Study that opened the chapter is motivated by research conducted in 1991 by Willerman, Schultz, Rutledge, and Bigler. Read about this study in the EESEE story “Brain Size and Intelligence,” and use what you have learned in this chapter to answer the following questions.

  1. 1. How did the researchers measure brain size? Is this a valid measure of brain size? Is it reliable? Is it biased?

  2. 2. How did the researchers measure intelligence? Is this a valid measure of intelligence?

  3. 3. The researchers found some evidence that brain size and intelligence are related. However, the study described in Example 8 did not. Discuss the differences in the two studies.

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image Online Resources

  • LearningCurve has good questions to check your understanding of the concepts.