A university surveyed recent graduates of the English department for their starting salaries. One hundred and ninety six graduates returned the survey. The average salary was $26,000. The population standard deviation was $1,450. What is the 95% confidence interval for the mean salary of all graduates from the English department?

A) [$25,988; $26,012]

B) [$24,550; $27,450]

C) [$25,804; $26,196]

D) [$25,797; $26,203]

The mean number of travel days per year for salespeople employed by three hardware distributors needs to be estimated with a 0.95 degree of confidence. For a small pilot study, the mean was 150 days and the standard deviation was 18 days. If the population mean is estimated within two days, how many salespeople should be sampled?

A)1,164

B) 311

C) 4,948

D)1,219

A research firm needs to estimate within 3% the proportion of junior executives leaving large manufacturing companies within three years. A 0.95 degree of confidence is to be used. Several years ago, a study revealed that 29% of junior executives left their company within three years. To update this study, how many junior executives should be surveyed?

A)1,067

B) 782

C) 764

D) 879