1 For a distribution of sample means constructed by sampling

1.) For a distribution of sample means constructed by sampling 6 items from a population of 19

-the sample size is 22

-there will be 27,132 possible sample means

-the mean of the sample means will be 4

-the standard error will be 1

2.) The mean weight of trucks traveling on a particular section of I-475 is not known. A state highway inspector needs an estimate of the mean. He selects a random sample of 49 trucks passing the weighing station and finds the mean is 17.6 tons, with a standard deviation of the sample of 4.7 tons. What is probability that a truck will weigh less than 14.8 tons?

-0.3383

-0.0333

-0.0

-0.0001

3.) An accounting firm is planning for the next tax preparation season. From last year\'s returns, the firm collects a systematic random sample of 100 filings. The 100 filings showed an average preparation time of 95 minutes with a standard deviation of 138 minutes. What is the probability that the mean completion time is between 1 and 2 hours, i.e., 58 and 121 minutes?

-Approximately 1

-0.9702

-0.9666

-0.4851

4.) The Intelligence Quotient (IQ) test scores are normally distributed with a mean of 109 and a standard deviation of 14. What is the probability that a person would score 131 or more on the test?

-0.4420

-0.9220

-0.0580

-0.9420

5.) The mean number of travel days per year for salespeople employed by hardware distributors needs to be estimated with a 0.86 degree of confidence. For a small pilot study the mean was 167 days and the standard deviation was 27 days. If the population mean is estimated within three days, how many salespeople should be sampled?

-538

-178

-2,138

-663

6.) The proportion of junior executives leaving large manufacturing companies within three years is to be estimated within 3 percent. The 0.95 degree of confidence is to be used. A study conducted several years ago revealed that the percent of junior executives leaving within three years was 24. To update this study, the files of how many junior executives should be studied?

-716

-779

-552

-1,349

7.) The mean weight of trucks traveling on a particular section of I-475 is not known. A state highway inspector needs an estimate of the mean. He selects a random sample of 47 trucks passing the weighing station and finds the mean weight is 21.9 tons. The population standard deviation is 3.2 tons. What is the 95 percent interval for the population mean? -22.0 and 23.8

-21.1 and 22.7

-21.3 and 22.5

-21.0 and 22.8

8.) Suppose 1,617 of 2,080 registered voters sampled said they planned to vote for the Republican candidate for president. Using the 0.95 degree of confidence, what is the interval estimate for the population proportion (to the nearest tenth of a percent)?

-76.6% to 78.9%

-76.0% to 79.5%

-76.2% to 79.2%

-77.0% to 80.5%

9.) A local company wants to evaluate their quality of service by surveying their customers. Their budget limits the number of surveys to 97. What is their maximum error of the estimated mean quality for a 94% level of confidence and an estimated standard deviation of 5?

-0.9544

-1.3149

-0.8377

-0.9661

10.) Recently, a university surveyed recent graduates of the English Department for their starting salaries. Four hundred graduates returned the survey. The average salary was $25,752. The population standard deviation is $2,553. What is the 95% confidence interval for the mean salary of all graduates from the English Department?

-[$25,423, $26,081]

-[$25,512, $27,268]

-[$25,541, $25,963]

-[$25,502, $26,002]

11.) A student wanted to construct a 95% confidence interval for the average age of students in her statistics class. She randomly selected 8 students. Their average age was 21.8 years with a standard deviation of 1.2 years. What is the best point estimate for the population mean?

-2.2 years

-1.2 years

-8 years

-21.8 years

12.) A pharmaceutical company wanted to estimate the population mean of monthly sales for their 250 sales people. 44 sales people were randomly selected. Their mean monthly sales was $10,908 with a population standard deviation of $1,044. Construct a 95% confidence interval for the population mean.

-[10,612.1, 11,203.9]

-[10,648.3, 11,167.7]

-[10,599.5, 11,216.5]

-[10,706.5, 11,109.5]

13.) A survey of households in a small town showed of 2,028 sampled households, that in 858 households at least one member attended a town meeting during the year. Using the 99% level of confidence, what is the confidence interval for the proportion of households represented at a town meeting?

-[0.4025, 0.4437]

-[0.4016, 0.4446]

-[0.3948, 0.4514]

-[0.4050, 0.4412]

14.) The manager of the local Hamburger Express wishes to estimate the mean time customers spend at the drive-through window. A sample of 20 customers experienced a mean waiting time of 2.65 minutes, with a standard deviation of 0.45 minutes. Develop a 90 percent confidence interval for the mean waiting time. (Round your answers to 4 decimal places.)

Solution

1, there will be 27132 sample means

2. probability = 0.3383