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STAT 104 Section 9

STAT 104 Section 9. Daniel Moon. Why Plus Four?. SE p of plus four are more stable!. Plus four works for confidence interval But for hypothesis testing, don’t use plus four. Agenda. Tests of Population mean μ X Comparisons of two means F-test for equal variances

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STAT 104 Section 9

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  1. STAT 104 Section 9 Daniel Moon

  2. Why Plus Four? SEp of plus four are more stable! Plus four works for confidence interval But for hypothesis testing, don’t use plus four

  3. Agenda • Tests of Population mean μX • Comparisons of two means • F-test for equal variances • Chi-square independence test • Prep for Midterm II • Go over Practice Exam

  4. Tests of Population mean μX <Alan> • Has the average price of homes increased since the 2000 census reported mean and SD figures? • A survey in India showed birthweights had an average of 111 and SD of 16 ounces • The national Latin Achievement test has a mean of 600 and SD of 50; Do students from Boston Latin School score above the national average on this test?

  5. Agenda • Tests of Population mean μX • Comparisons of two means • F-test for equal variances • Chi-square independence test • Prep for Midterm II

  6. Comparisons of two means <Alan> • To determine if the length of commercials on public television increased in the past 10 years, tapes of some programs in 1996 and 2006 were analyzed • Surveys were conducted to determine if adults from MA are saving more or less than those from NY • Were airlines justified last month when they raised ticket prices due to an increase in passenger weight?

  7. Agenda • Tests of Population mean μX • Comparisons of two means • F-test for equal variances • Chi-square independence test • Prep for Midterm II

  8. F-test for equal variances • Test statistics F = larger s^2 / smaller s^2 • When you calculate p-value, • Don’t forget to multiply by 2 if it’s two-tail. <Alan>

  9. Agenda • Tests of Population mean μX • Comparisons of two means • F-test for equal variances • Chi-square independence test • Prep for Midterm II

  10. Chi-square independence test <Alan> • A survey was conducted to determine if the poverty rate for 1st generation immigrants from Brazil is the same in northern and southern states

  11. Agenda • Tests of Population mean μX • Comparisons of two means • F-test for equal variances • Chi-square independence test • Prep for Midterm II

  12. Prep for Midterm II • Write down your notation clearly, your hypotheses, your bounds for condence intervals, your rejection region, your estimates, your bounds for condence intervals, your rejection region, your estimates for sample statistics • Draw an approximate normal curve if you can to test yourself and make sure you are taking the right numbers (interior, tails, etc) from the table. Adequate chi2, F, t, Z tables will be provided, but you will often have to approximate. • Stating reasons for your choices is the best way to get credit. Yes there will be questionable moments as to which test/tails to use (as there are in real life!).

  13. Prep for Midterm II

  14. Tees (2007 Spring Midterm II. #2) • Stinger tees > Regular tees

  15. TV (2007 Spring Midterm II. #2) • Sufficient evidence to show that the time men now spend watching sports on TV is different from that in 1990?

  16. Hepatitis (2007 Spring Midterm II. #4) Determine if the risk of Hepatitis C was related to whether people had a tattoo? Relative risk of hepatitis C associated with having a tattoo

  17. Hepatitis (2007 Spring Midterm II. #5) • 2000 US census • # of people per household • Average: 2.5 , s.d. = 2 • Concern that this average has continued to drop since 2000.

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