13.

[0/3 Points]DETAILSPREVIOUS ANSWERSASWSBE14 8.TB.2.032.

MY NOTES

ASK YOUR TEACHER

PRACTICE ANOTHER

You may need to use the appropriateappendix tableortechnologyto answer this question.

A random sample of84airline pilots recruited by an airline service had an average yearly income of $99,700with a standard deviation of$11,000.

(a)

If we want to determine a 95% confidence interval for the average yearly income of the population, what is the value oft? (Round your answer to three decimal places.)

t=

(b)

Develop a 95% confidence interval for the average yearly income of all pilots (in dollars). (Round your answers to the nearest dollar.)

$ to $

14.

[-/4 Points]DETAILSASWSBE14 8.TB.2.036.

MY NOTES

ASK YOUR TEACHER

PRACTICE ANOTHER

You may need to use the appropriateappendix tableortechnologyto answer this question.

Two hundred students are enrolled in an Economics class. After the first examination, a random sample of 6 papers was selected. The scores were68,74,89,71,72, and82.

(a)

Determine the standard error of the mean. (Round your answer to four decimal places.)

(b)

What assumption must be made before we can determine an interval for the mean score of all the students in the class? Explain why.

Sincenis small andis estimated froms,we must assume the distribution of all the scores is normal.Sincenis small andis estimated froms,we must assume thatsis greater thann. Sincenis small andis estimated froms,we must assume thatnis greater thans.Since the distribution of all scores is not normal we must assume=s.Sincenis small andis estimated froms,we must assume thatxis greater thans.

(c)

Assume the assumption of Part b is met. Provide a 95% confidence interval for the mean score of all the students in the class. (Round your answers to two decimal places.)

to