A random sample of 42 college graduates revealed that they worked an average of 5.5 years on the job before being promoted. The sample standard deviation was 1.1 years. Using the 0.99 degree of confidence, what is the confidence interval for the population mean? Mulial-

A study of 40 English professors showed that they spend, on average, 12.6 minutes correcting a student's term paper. The standard deviation was 2.5 minutes. Construct the 99% confidence interval of the mean for all term papers.

In a random sample of 17 people, the mean commute time to work was 30.2 minutes and the standard deviation was 7.1 minutes. Assume the population is normally distributed and use a t- distribution to construct a 95% confidence interval for the population mean y. What is the margin of error of y? Interpret the results.

a group of 59 randomly selected students have a mean score of 29.5 with a standard deviation of 5.2 on a placement test. what is the 90% confidence interval for the mean score, u, of all students taking the test?

A random sample of 90 group leaders, supervisors, and similar personnel revealed that a person spent an average of 5.5 years on the job before being promoted. The population standard deviation was 1.8 years. Using the 0.95 degree of confidence, what is the confidence interval for the population mean?

A labor department wants to study mean age of all people in the civilian labor force. The average age of 49 randomly selected people in the civilian labor force is found to be 35.6 years. Assuming the population standard deviation is 11, what is the 95% confidence interval for true population mean?

A study of 390 kindergarten students showed that they have seen on average 4500 hours of television. If the sample standard deviation is 800, find the 95% confidence level of the mean for all students. If a parent claimed that his children watched only 3800 hours, would the claim be believable? (a sample normal distribution – is the chart value below 5%?)