Table 11-1 includes more recent data (based on “Autism Occurrence by MMR Vaccine Status Among U.S. Children with Older Siblings With and Without Autism,” by Jain et al., Journal of the American Medical Association, Vol. 313, No. 15). The 1878 subjects included in Table 11-1 were all children of age 4 with an older sibling having autism, and those who were vaccinated received one dose of the vaccine MMR (for measles, mumps, and rubella). In their conclusion, the authors of the study stated “these findings indicate no harmful association between MMR vaccine receipt and ASD (autism spectrum disorder) even among children already at higher risk for ASD.” Do the data in Table 11-1 support this conclusion? That is, among four-year-old children, does having autism appear to be independent of whether the children are unvaccinated or vaccinated? Chapter Objectives 577 TABLE 11-1 Results From a Study of a Link Between the MMR Vaccine and Autism Unvaccinated Vaccinated Autism 25 64 No Autism 362 1427 CHAPTER OBJECTIVES Chapters 7 and 8 introduced important methods of inferential statistics, including confidence intervals for estimating population parameters (Chapter 7) and methods for testing hypotheses or claims (Chapter 8). In Chapter 9 we considered inferences involving two populations, and in Chapter 10 we considered inferences involving correlation and regression with paired data. In this chapter we use statistical methods for analyzing categorical (or qualitative, or attribute) data that can be separated into different cells. The methods of this chapter use the same x2 (chi-square) distribution that was introduced in Section 7-3 and again in Section 8-4. See Section 7-3 or Section 8-4 for a quick review of properties of the x2 distribution. Here are the chapter objectives: 11-1 Goodness-of-Fit • Use frequency counts of categorical data partitioned into different categories and determine whether the data fit some claimed distribution. 11-2 Contingency Tables • Use categorical data summarized as frequencies in a two-way table with at least two rows and at least two columns to conduct a formal test of independence between the row variable and column variable. • Be able to conduct a formal test of a claim that different populations have the same proportions of some characteristics. S
RkJQdWJsaXNoZXIy NjM5ODQ=