2201_Quiz4

2201_Quiz4 - Revised 2201_Quiz4m EXST 2201 Quiz 4 Name...

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Unformatted text preview: Revised 01/19/2010 2201_Quiz4.docm EXST 2201 Quiz 4 Name: Section: Score: Directions: This quiz will be available on Moodle after the lectures for chapter 10 have been given. Mark your answers on this printout. When the quiz is available on Moodle, record your answers in the Moodle quiz and submit them for grading. You may take the quiz only once and you will have an hour and a half to complete it, so be sure of your answers before you start the Moodle quiz. 1. Previous research shows that 65% of murders are committed with a firearm. If 150 murders are randomly selected, use the normal approximation to the binomial to determine what is the probability that: 1A. 100 or more murders are committed with a firearm? • • • • 0.452 0.548 0.367 0.164 1B. 90 or fewer murders are committed with a firearm? • • • • 0.115 0.367 0.164 0.452 1C. 100 ≤ murders ≤ 105 are committed with a firearm? • • • • 0.452 0.548 0.115 0.282 Page 1 of 5 Revised 01/19/2010 2201_Quiz4.docm 2. In a poll of 2,208 randomly selected Americans, 1,247 thought that state laws regarding child safety restraints in vehicles should be strengthened. 2A. What is the point estimate of the population proportion? • • • • 1.77 0.19 0.50 0.56 2B. What is the value of the condition to use the normal approximation? • • • • 1,247 544 –3,012 306 2C. Is it appropriate to compute a CI estimate of proportion when the condition to use the normal approximation is 6.8345? • • • • Yes. No. Sometimes. Depends on distribution. 2D. What is the 92% CI estimate of proportion? • • • • (0.54, 0.60) (0.54, 0.56) (0.54, 0.58) (0.55, 0.57) Page 2 of 5 Revised 01/19/2010 2201_Quiz4.docm 3. A study finds that 85% of teachers use the Internet to teach. A researcher claims that the percentage has recently increased. She collects a random sample of 340 teachers and finds that 302 of the teachers used the Internet to teach. 3A. What is the population proportion (p) and the sample proportion ( ) for this set of data? • • • • 0.89, 0.85 0.85, 0.89 0.85, 0.85 0.89, 1.12 3B. What is the magnitude of the critical value for a one-tailed test of proportion with significance 0.10? • • • • 2.33 1.75 1.64 1.28 3C. What is the value of the test statistic to test if the population proportion is 0.85 at significance 0.10? • • • • –1.75 1.55 2.06 2.47 3D. What decision would be made for a one-tailed test that the population proportion is 0.85 at significance 0.10? • • • • Do not reject the null. Reject the null. Sometimes reject the null. Do not reject the alternative. Page 3 of 5 Revised 01/19/2010 2201_Quiz4.docm 4. On average it has been found in grocery stores that 1% of scanned items are priced incorrectly. Recently, a sample of 1,034 randomly selected items were scanned and 20 were found to be priced incorrectly. Has the rate of incorrectly priced items changed? 4A. What is the appropriate test procedure? • • • • z-Test of the mean. t-Test of the mean. z-Test of the proportion. None of these. 4B. What is the appropriate null hypothesis? • • • • µ = 0.01 µ ≤ 0.01 µ ≠ 0.01 µ ≥ 0.01 4C. What is the appropriate alternative hypothesis? • • • • µ = 0.01 µ < 0.01 µ ≠ 0.01 µ > 0.01 4D. Assume it should be a t-test and the sample size is 105. What decision would be made for a hypothesis test at significance 0.05 if you calculated a test statistic of 0.94? • • • • Do not reject the null. Reject the null. Sometimes reject the null. Do not reject the alternative. Page 4 of 5 Revised 01/19/2010 2201_Quiz4.docm 5. In the initial test of the Salk vaccine for polio, 400 children were selected and divided into two groups of 200. One group was vaccinated with the Salk vaccine while the second group was vaccinated with a placebo. Of those vaccinated with the Salk vaccine, 33 later developed polio. Of those vaccinated with the placebo, 115 later developed polio. Test the claim that the Salk vaccine is effective in lowering the rate of polio. Use significance 0.01 and assume that the data are distributed normally. 5A. What is the appropriate set of hypotheses (H0, H1)? • • • • psalk – pplacebo = 0, psalk – pplacebo ≠ 0, psalk – pplacebo = 0, psalk – pplacebo = 0, psalk – pplacebo ≠ 0 psalk – pplacebo = 0 psalk – pplacebo < 0 psalk – pplacebo > 0 5B. What are the correct proportions (psalk, pplacebo)? • • • • 0.095, 0.435 0.575, 0.165 0.165, 0.575 0.435, 0.095 5C. What is the correct value of the test statistic? • • • • –0.23 –1.38 –9.54 –8.49 5D. What is the correct confidence interval? • • • • (–0.52, –0.30) (–0.30, 0.52) (–0.53, 0.30) (0.30, 0.53) 5E. Was the Salk vaccine effective at reducing the rate of polio? • • • • Yes. No. Sometimes. Depends on distribution. Page 5 of 5 ...
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