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Statistics 400 - Lecture 15

Statistics 400 - Lecture 15. Today: 10.1-10.3 Assign #5: 8.62, 8.70, 8.78, and

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Statistics 400 - Lecture 15

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  1. Statistics 400 - Lecture 15

  2. Today: 10.1-10.3 • Assign #5: 8.62, 8.70, 8.78, and • In recent years, there has been growing concern about the health effects of video display terminals (VDTs). It is known that the miscarriage rate of a pregnancy under normal conditions is about 20%. In a survey of 15 part-time female employees who used VDTs at least 20 hours per week, there were 5 reported miscarriages. At the 1% significance level, is there evidence that exposure to VDTs is increasing the miscarriage rate? • Due next Thursday

  3. Example: • An insurance company want to know if the average speed at which men drive is greater than that of women drivers • The company took a random sample of 22 cars driven by men on a highway and recorded the average speed of each driver • The company took another random sample of 14 cars driven by women on the same highway and recorded the average speed of each driver • How might you go about testing the hypothesis?

  4. Inferences about Two Population Means • Situation: • Have 2 independent random samples • Each sample comes from a normal population • The population standard deviations are equal • Want to test test a hypothesis about the population means

  5. Example (continued): • The hypothesis we wish to test is:

  6. Test Statistic: • Where • When H0is true, t has a t-distribution with (n1+n2- 2) degrees of freedom

  7. Computing a P-Value • P-Value depends on the alternative

  8. Putting it all together • Example: • Insurance company wants to know if average speed at which men drive is greater than women drivers • Company took a random sample of 22 cars driven by men on a highway and recorded the average speed of each driver • They took another random sample of 14 cars driven by women on the same highway and recorded the average speed of each driver

  9. Data:

  10. Sample Statistics

  11. Hypothesis: • Test Statistic: • P-Value:

  12. Example:Gender Differences in Metered-Dose Inhaler-Spacer (MDI) Device Technique (Pharmacotherapy, 2000) • Asthma is a disease of chronic airway inflamation • A typical treatment for asthma is using inhaled formulations (e.g., corticosteroids) • Proper usage consists of shaking the inhaler, slowly depressing the cannister and simultaneously inhaling over 3-5 seconds and then holding in the breath for 10 seconds • Study in 1990’s indicated gender differences in the usage of the MDI

  13. Example:Gender Differences in Metered-Dose Inhaler-Spacer (MDI) Device Technique (Pharmacotherapy, 2000) • Study performed to determine whether gender affects the correct use of MDI device • 83 3rd year Doctor of Pharmacy students (31 men; 52 women) were given a placeobo MSI and 20 minutes training on the device • One week later, the students returned and were tested on their ability to use the device…each student was assigned a score in usage by the tester • Mean score for males was 8.68 and mean score for women was 8.65 with sample standard deviations of 3.62 and 4.00 respectively • What do these data indicate?

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