*13. Forty volunteers participate in an experiment on attitude change. An attitude item is completed by these individuals both before and after they watch a spirited debate on the topic. The following data are obtained:

390 Chapter 18 Making Inferences From Frequency Data Response to Attitude Statement Agree Undecided Disagree Before 8 20 12 After 18 12 10 The researcher calculates 2 ¼ 6:03 and, because 2:

05 ¼ 5:99, rejects the null hypothesis of independence. After calculating the obtained proportions within each of the six cells in this 2  3 contingency table (i.e., fo 7 row total), the researcher concludes that watching the debate seems to have shifted many of the \undecided" individuals into the \agree" category. What critical mistake did this researcher make?