Statistics
bk97
hw8.docxThe z value associated with a two-sided 88% confidence interval is _______.
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1.90 |
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1.28 |
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1.55 |
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1.17 |
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0.88 |
Suppose a researcher is interested in understanding the variation in the price of store brand milk. A random sample of 36 grocery stores selected from a population and the mean price of store brand milk is calculated. The sample mean is $3.13 with a population standard deviation of $0.23. Construct a 92% confidence interval to estimate the population mean.
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$3.03 to $3.23 |
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$3.12 to $3.14 |
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$3.05 to $3.21 |
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$2.90 to $3.36 |
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$3.06 to $3.20 |
Brian Vanecek, VP of Operations at Portland Trust Bank, is evaluating the service level provided to walk-in customers. Accordingly, his staff recorded the waiting times for 64 randomly selected walk-in customers and determined that their mean waiting time was 15 minutes. Assume that the population standard deviation is 4 minutes. The 90% confidence interval for the population mean of waiting times is ________.
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13.86 to 16.14 |
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18.12 to 19.87 |
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14.27 to 15.73 |
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14.18 to 15.82 |
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9.88 to 20.12 |
James Desreumaux, VP of Human Resources of American First Banks (AFB), is reviewing the employee training programs of AFB banks. His staff randomly selected personnel files for 100 tellers in the Southeast Region and determined that their mean training time was 25 hours. Assume that the population standard deviation is 5 hours. The 88% confidence interval for the population mean of training times is ________.
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24.42 to 25.59 |
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17.25 to 32.75 |
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19.15 to 30.85 |
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21.00 to 32.00 |
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24.23 to 25.78 |
A researcher is interested in estimating the mean weight of a semi trailer truck to determine the potential load capacity. She takes a random sample of 17 trucks and computes a sample mean of 20,000 pounds with sample standard deviation of 1,500. She decides to construct a 98% confidence interval to estimate the mean. The degrees of freedom associated with this problem are _______.
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16 |
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15 |
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20 |
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18 |
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17 |
A researcher is interested in estimating the mean weight of a semi trailer truck to determine the potential load capacity. She takes a random sample of 17 trucks and computes a sample mean of 20,000 pounds with sample standard deviation of 1,500. The 95% confidence interval for the population mean weight of a semi trailer truck is ______________.
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19,232 to 20,768 |
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19,365 to 20,635 |
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19,367 to 20,633 |
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19,229 to 20,771 |
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18,500 to 21,500 |
The weights of aluminum castings produced by a process are normally distributed. A random sample of 5 castings is selected; the sample mean weight is 2.21 pounds; and the sample standard deviation is 0.12 pound. The 98% confidence interval for the population mean casting weight is _________.
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2.00 to 2.41 |
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1.76 to 2.66 |
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2.08 to 2.34 |
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2.49 to 2.67 |
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1.93 to 2.49 |
A researcher wants to estimate the proportion of the population which possesses a given characteristic. A random sample of size 1800 is taken resulting in 450 items which possess the characteristic. The point estimate for this population proportion is _______.
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0.35 |
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0.25 |
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0.15 |
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0.55 |
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0.45 |
A large national company is considering negotiating cellular phone rates for its employees. The Human Resource department would like to estimate the proportion of its employee population who own an Apple iPhone. A random sample of size 250 is taken and 40% of the sample own an iPhone. The 90% confidence interval to estimate the population proportion is ____.
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0.34 to 0.46 |
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0.37 to 0.43 |
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0.35 to 0.45 |
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0.39 to 0.41 |
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0.40 to 0.45 |
A large trucking company wants to estimate the proportion of its trailer truck population with refrigerated carrier capacity. A random sample of 200 trailer trucks is taken and 30% of the sample have refrigerated carrier capacity. The 90% confidence interval to estimate the population proportion is _______.
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0.53 to 0.67 |
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0.33 to 0.39 |
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0.24 to 0.36 |
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0.27 to 0.33 |
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0.25 to 0.35 |
A random sample of 225 items from a population results in 60% possessing a given characteristic. Using this information, the researcher constructs a 99% confidence interval to estimate the population proportion. The resulting confidence interval is _______.
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0.54 to 0.66 |
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0.57 to 0.63 |
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0.52 to 0.68 |
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0.68 to 0.76 |
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0.59 to 0.61 |
Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS e-mail for non-business communications. A random sample of 200 e-mail messages was selected. Thirty of the messages were not business related. The 90% confidence interval for the population proportion is _________.
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0.108 to 0.192 |
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0.153 to 0.247 |
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0.091 to 0.209 |
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0.145 to 0.255 |
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0.255 to 0.265 |
The following random sample was selected from a normal distribution: 4.5, 6.4, 2.3, 1.8, 5.3, then the 95% confidence interval to estimate the population mean is between __________.
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2.37 and 5.78 |
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3.23 and 4.89 |
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4.19 and 7.09 |
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1.62 and 6.50 |
A department store finds that in a random sample of 200 customers, 60% of the sampled customers had browsed its website prior to visiting the store. Based on this data, a 90% confidence interval for the population proportion of customers that browse the store’s website prior to visiting the store will be between _________________.
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0.6588 and 0.6312 |
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0.5960 and 6040 |
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0.5978 and 0.6022 |
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0.5430 and 0.6570 |
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0.4528 and 0.5250 |
A national survey of companies included a question that asked whether the customers like the new flavor of a cola from company A. The sample results of 1000 customers, and 850 of them indicated that they liked the new flavor. The 98% confidence interval on the population proportion of people who like the new flavor is _______________.
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0.81 and 0.89 |
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0.83 and 0.87 |
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0.84 and 0.86 |
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0.82 and 0.88 |
Construct 90%, 95%, and 99% confidence intervals to estimate μ from the following data. State the point estimate. Assume the data come from a normally distributed population.
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12.1 |
11.6 |
11.9 |
12.9 |
12.5 |
11.4 |
12.0 |
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11.7 |
11.8 |
12.1 |
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(Round the intermediate values to 4 decimal places. Round your answers to 2 decimal places.) 90% confidence interval:
≤ μ ≤
95% confidence interval:
≤ μ ≤
99% confidence interval:
≤ μ ≤
The point estimate is
Use the following information to compute the confidence interval for the population proportion. a. n = 715 and x = 329, with 95% confidence b. n = 284 and p̂ = .71, with 90% confidence c. n = 1250 and p̂ = .48, with 95% confidence d. n = 457 and x = 270, with 98% confidence (Round your answers to 4 decimal places.) a.
≤ p ≤
b.
≤ p ≤
c.
≤ p ≤
d.
≤ p ≤
≤ µ ≤
