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1. The average time it takes for a person to experience
pain relief from aspirin is 25 minutes. A new ingredient is added to help speed up relief. Let µ denote the average time to obtain pain relief with the new product. An experiment is conducted to verify if the new product is better. What are the null and alternative hypotheses? (a) H0 : µ = 25 vs. Ha : µ 25 (GO TO 2) (b) H0 : µ = 25 vs. Ha : µ < 25 (GO TO 6) (c) H0 : µ < 25 vs. Ha : µ = 25 (GO TO 8) (d) H0 : µ < 25 vs. Ha : µ > 25 (GO TO 5) (e) H0 : µ = 25 vs. Ha : µ > 25 (GO TO 4) 2. A significance test was performed to test the null
hypothesis H0 : µ = 2 versus the alternative
Ha: µ > 2. The test statistic is z = 1.40. The P-value
for this test is approximately
(a) 0.16 (GO TO 5)
(b) 0.08 (GO TO 8)
(c) 0.003 (GO TO 1)
(d) 0.92 (GO TO 6)
(e) 0.70 (GO TO 3)
3. In a test of H0: µ = 100 against Ha: µ 100, a sample of size 10 produces a sample mean of 103 and a P-value of 0.08. Thus, at the 0.05 level of significance (a) there is sufficient evidence to conclude that µ 100. (b) there is sufficient evidence to conclude that µ = 100. (c) there is insufficient evidence to conclude that µ = 100. (d) there is insufficient evidence to conclude that µ 100. (e) there is sufficient evidence to conclude that µ = 103. 4. To determine the reliability of experts used in interpreting
the results of polygraph examinations in criminal investigations, 280 cases were studied. The results were True Status
Innocent Guilty
Examiner’s “Innocent” 131 15
Decision “Guilty” 9 125
If the hypotheses were H0: suspect is innocent vs. Ha: suspect is guilty, then we could estimate the probability of making a Type II error as (a) 15/280 (GO TO 8) (b) 9/280 (GO TO 3) (c) 15/140 (GO TO 1) (d) 9/140 (GO TO 6) (e) 15/146 (GO TO 5) 5. A certain population follows a Normal distribution
with mean and standard deviation
You obtain a P-value of 0.022. Which of the following is true? (a) A 95% confidence interval for will include the value 1. (b) A 95% confidence interval for will include the value 0. (c) A 99% confidence interval for will include the value 1. (d) A 99% confidence interval for will include the value 0. (e) None of these is necessarily true. (GO TO 2) 6. Vigorous exercise helps people live several years longer (on
the average). Whether mild activities like slow walking extend life is not clear. Suppose that the added life expectancy from regular slow walking is just 2 months. A statistical test is more likely to find a significant increase in mean life if It is based on a very large random sample and a 5% significance level is used. (GO TO 2) It is based on a very large random sample and a 1% significance level is used. (GO TO 1) It is based on a very small random sample and a 5% significance level is used. (GO TO 8) It is based on a very small random sample and a 1% significance level is used. (GO TO 3) The size of the sample doesn't have any effect on the significance of the test. (GO TO 4) 7. Which of the following is not a condition for performing
(a) Inference is based on n independent measurements. (b) The population distribution is Normal or the sample size is large (say n > 30). (GO TO 5) (c) To use a z test, we must know the population standard (d) The data are obtained from an SRS from the population (e) Both np and n(1 – p) are 10 or greater. (GO TO 3) 8. Does taking ginkgo tablets twice a day provide significant improvement in mental performance? To investigate this issue, a researcher conducted a study with 150 adult subjects who took ginkgo tablets twice a day for a period of six months. At the end of the study, 200 variables related to the mental performance of the subjects were measured on each subject and the means compared to known means for these variables in the population of all adults. Nine of these variables were significantly better (in the sense of statistical significance) at the = 0.05 level for the group taking the ginkgo tablets as compared to the population as a whole, and one variable was significantly better at the = 0.01 level for the group taking the ginkgo tablets as compared to the population as a whole. It would be correct to conclude that (a) there is very good statistical evidence that taking ginkgo tablets twice a day provides some improvement in (b) there is very good statistical evidence that taking ginkgo tablets twice a day provides improvement for the variable that was significant at the = 0.01 level. We should be cautious about making claims for the variables that were significant at the = 0.05 level. (GO TO 1) (c) these results would have provided very good statistical evidence that taking ginkgo tablets twice a day provides some improvement in mental performance if the number of subjects had been larger. It is premature to draw statistical conclusions from studies in which the number of subjects is less than the number of variables measured. (GO TO 5) (d) there is very good statistical evidence that taking ginkgo tablets twice a day provides significant improvement in ten specific areas related to mental condition. (GO TO 2)

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