Unformatted text preview: victims could instead be spent on providing basic health care to the many Americans who lack it. Statistics alone rarely settles complicated questions such as “Which kind of health care system works better?” 8 M316 Chapter 23 Dr. Berg Exercise (23.8) Attitudes Toward Recycled Products In Exercises 23.2 and we began to analyze data on consumer attitudes toward recycled products. Here is the CrunchIt! output. a) Starting from the observed and expected counts, find the six terms of the chi‐ square statistic and then the statistic Χ2 itself. Check your work against the computer output. b) What is the P‐value for the test? Explain what it means to reject H0. c) Which cells contribute the most to Χ2? What kind of relationship do these point to? Cell Counts Required for the Chi‐Square Test The chi‐square test, like the z test is an approximation that becomes more accurate as the cell counts increase. Fortunately, the chi‐square approximation is accurate for quite modest counts. Here is a practical guideline. 9 M316 Chapter 23 Dr. Berg Cell Counts Required for the Chi‐Square Test You can safely use the chi‐square test with critical values from the chi‐square distribution when no more than 20% of the expected counts are less than 5 and all individual counts are 1 or greater. In particular, all four expected counts in a 2 by 2 table should be 5 or greater Exercise (23.10) Does Chi‐Square Apply? Verify that the data in Exercise 23.8 meet the guideline. Uses of the Chi‐Square Test Two‐way tables can arise in several ways. Example (23.5) Extracurricular...
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This note was uploaded on 09/02/2010 for the course BIO 325 taught by Professor Saxena during the Spring '08 term at University of Texas.
- Spring '08