Quiz Stat

Name: [pic]_________________________ 1. Two events are complementary when A) the sum of their probabilities is one. B) the joint probability of the two events is one. C) they are mutually exclusive. D) None of the above. 2. Are Service provider and county independent events? A) Yes. B) No. C) Insufficient information to determine. 3. A random variable is a function or rule that assigns a numerical value to each outcome in the sample space of a stochastic experiment. True A) False 4. A probability distribution A) is a listing of all possible values of a random variable.B) is a listing of all possible values of a random variable, along with their probabilities. C) can assume values between -1 and +1. D) has none of the above properties. 5. For a continuous random variable, the total area beneath the probability distribution curve will be greater than 0 but less than 1. A) True False 6. The standardized normal distribution always has a mean of zero and a standard deviation of one. True A) False 7. Excel’s RAND() function produces random numbers that are uniformly distributed from 0 to 1. The standard deviation of this distribution is about A) . 5000B) . 2500 C) . 3333 D) . 2887 8. The expected value of an unbiased estimator is equal to the parameter whose value is being estimated. True A) False [pic] 9. All estimators are biased since sampling errors always exist to some extent. A) True False 10. The Central Limit Theorem says that, if n exceeds 30, a histogram of the sample will have a bell-shape, even if the population isn't normal. A) True False 11. The distribution of the sample proportion p=x/n is normal when n ;/- 30. A) True False 12. The standard error of the mean decreases when the A) sample size decreases.B) standard deviation increases if n is constant. C) standard deviation decreases and n increases. D) population size decreases. 13. The owner of Limp Pines Resort wanted to know the average age of its clients. A random sample of 25 tourists is t aken. It shows a mean age of 46 years with a standard deviation of 5 years. The width of a 98 percent CI for the true mean client age is approximately ____ years. A) +/- 2. 06 B) +/- 2. 33 C) +/- 2. 49 D) +/- 2. 79 14. In a right-tail test, a statistician came up with a z test statistic of 1. 469. What is the p-value? A) . 4292 B) . 0708 C) . 0874 D) . 0301 15.To estimate the average annual expenses of students on books and class materials a sample of size 36 is taken. The average is $850 and the standard deviation is $54. A 99% confidence interval for the population mean is A) $823. 72 to $876. 28 B) $832. 36 to $867. 64 C) $826. 82 to $873. 18 D) $825. 48 to $874. 52 16. A poll showed that 48 out of 120 randomly chosen graduates of California medical schools last year intended to specialize in family practice. What is the width of a 90% confidence interval for the proportion that plan to specialize in family practice? A) +/- . 04472 B) +/- . 07357 C) +/- . 8765 D) +/- . 00329 17. In a random sample of 810 women employees, it is found that 81 would prefer working for a female boss. The width of the 95% confidence interval for the proportion of women who prefer a female boss is A) +/- . 0288 B) +/- . 0105 C) +/- . 0196 D) +/- . 0207 [pic] 18. Jolly Blue Giant Health Insurance (JBGHI) is concerned about rising lab test costs and would like to know what proportion of the positive lab tests for prostate cancer are actually proven correct through subsequent biopsy. JBGHI demands a sample large enough to ensure an error of +/- 2% with 90% confidence.What is the necessary sample size? A) 2,401 B) 1,692 C) 1,604 D) 609 [pic]19. A financial institution wishes to estimate the mean balances owed by its credit card customers. The population standard deviation is estimated to be $300. If a 98 percent confidence interval is used and an interval of +/- $75 is desired, how many cardholders should be sampled? A) 3382 B) 62 C) 629 87 20. For a one-tailed test of hypothesis for a single population mean with 13 degrees of freedom, the value of the test statistic was 1. 863. The p-value is A) between . 05 and . 025. B) between . 10 and . 05 C) greater than . 10 D) less than . 001.