1 The mean number of travel days per year for salespeople em

1. The mean number of travel days per year for salespeople employed by hardware distributors needs to be estimated with a 0.66 degree of confidence. For a small pilot study the mean was 163 days and the standard deviation was 23 days. If the population mean is estimated within two days, how many salespeople should be sampled?

2. The proportion of junior executives leaving large manufacturing companies within three years is to be estimated within 5 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 25. To update this study, the files of how many junior executives should be studied?

3. Suppose 1,558 of 2,019 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)?

4. A local company wants to evaluate their quality of service by surveying their customers. Their budget limits the number of surveys to 95. What is their maximum error of the estimated mean quality for a 81% level of confidence and an estimated standard deviation of 5?

5. Recently, a university surveyed recent graduates of the English Department for their starting salaries. Four hundred graduates returned the survey. The average salary was $25,869. The population standard deviation is $2,576. What is the 95% confidence interval for the mean salary of all graduates from the English Department?

Solution