Qusetion: The raw data for Example can be thought of as two categorical variables (with two possible categories each) for each participant in the experiment. What are the two variables and their categories? Construct a contingency table in the format learned in Chapter 4, with the explanatory variable as rows. In Chapter 4, you learned how to look for relationships by finding a chi-square statistic and associated p-value. In the context of this example, how do you think the null and alternative hypotheses would be stated if the problem is viewed from that perspective?

Example: The Prevention of Ear Infections On the basis of its biochemical properties, Finnish researchers hypothesized that regular use of the sweetener xylitol might be useful for preventing ear infections in preschool children and carried out a study to test this hypothesis (Uhari, 1998).