Practice
4
1. If the 95% confidence limits for the turns out to be 6.5 and 8.5 it means a. The probability is .95 that x falls between 6.5 and 8.5 b. The probability is that x falls between 6.5 and 8.5 c. The probability is .95 that the interval contains . d. 4 =8.5-6.5 2. If a sample size of 16 yields an average of 12 and a standard deviation of 3, estimate the 95% CI for the mean a. 10.4, 13.6 b. 10.45, 13.55 c. 10.53, 13.47 d. 10.77, 13.23 3. Suppose 95% confidence interval for µ turns out to be (1000, 2100). To make more useful inferences from the data, it is desired to reduce the width of the confidence interval. Which of the following will result in reduced interval width? a. Increase the sample size. b. Decreases the confidence level. c. Increase the sample size and decrease the confidence le vel. d. Increase the confidence level and decrease the sample s ize. 4. The 95% confidence interval estimate of the mean time taken to process a new insurance policy is 11 ≤ µ ≤ 12 days. Which one of the following statement is true? a. Only 5% of all policies take less than 11 days or more than 12 days to process. b. Only 5% of all policies take between 11 and 12 days to process.
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Transcript of Practice
1. If the 95% confidence limits for the turns out to be 6.5 and 8.5 it means
a. The probability is .95 that x falls between 6.5 and 8.5b. The probability is that x falls between 6.5 and 8.5c. The probability is .95 that the interval contains .d. 4 =8.5-6.5
2. If a sample size of 16 yields an average of 12 and a standard deviation of 3, estimate the 95% CI for the mean
a. 10.4, 13.6b. 10.45, 13.55c. 10.53, 13.47d. 10.77, 13.23
3. Suppose 95% confidence interval for µ turns out to be (1000, 2100). To make more useful inferences from the data, it is desired to reduce the width of the confidence interval. Which of the following will result in reduced interval width?
a. Increase the sample size. b. Decreases the confidence level. c. Increase the sample size and decrease the confidence level. d. Increase the confidence level and decrease the sample size.
4. The 95% confidence interval estimate of the mean time taken to process a new insurance policy is 11 ≤ µ ≤ 12 days. Which one of the following statement is true?
a. Only 5% of all policies take less than 11 days or more than 12 days to process. b. Only 5% of all policies take between 11 and 12 days to process.c. About 95 out of every 100 intervals similarly constructed from samples of same
size will contain the true mean value. d. The probability is 0.95 that µ lies between 11 and 12 days.e. All of the above.
5. Given sample statistics of X = 70, s = 12, and n = 64, the point estimate of the population mean and the 95 percent confidence interval are
a. Point estimate = 72 and 95 percent confidence interval equal to 72 ± 2.94b. Point estimate = 72 and 95 percent confidence interval equal to 72 ± 0.37c. Point estimate = 70 and 95 percent confidence interval equal to 70 ± 0.37d. Point estimate = 70 and 95 percent confidence interval equal to 70 ± 2.94e. None of the above is correct.
6. A call center manager measures the standard deviation in waiting time for a random sample of 16 customers to be 80 (seconds). Assuming that the waiting times are normal, what is the 95 percent confidence interval for the population variance?
a. 2160.32 to 21533.25b. 163.21 to 5493.10c. 781.59 to 10118.64d. 5127.53 to 31045.77e. None of the above is correct.
1.c2.a
