SAMPLE THEORY AND HYPOTHESIS TESTING

A recent study showed that the modern working person experiences an average of 2.1 hours per

day of distractions (phone calls, e-mails, impromptu visits, etc.). A random sample of 50 workers for a large firm

found that these workers were distracted an average of 1.8 hours per day and the population standard

deviation was 20 minutes.

a)

time.

Estimate the 95% confidence interval of the mean population distraction

[2 marks]

b)

Interpret your results

[2 marks]

An administrator at Cornwall Regional hospital wishes to estimate the birth weights of infants.

How large a sample must be obtained if she desires to be 99% confident that the true mean is within 2 ounces

of the sample mean? Assume 0 = 8 ounces.

The Student Loan Bureau conducted a survey of 1404 respondents and found that 323 students

paid for their education by student loans.

The Student Loan Bureau conducted a survey of 1404 respondents and found that 3 Time left 0:52:48

paid for their education by student loans.

a)

student loans.

Find the 90% confidence interval of the true proportion of students who paid for their education by

b)

Interpret your results

IV

A special cable has a breaking strength of 800 pounds. The standard deviation of the population is

12 pounds. A researcher selects a sample of 36 cables and finds that the average breaking strength is 795

pounds.

Can he reject the claim that the breaking strength is 800 pounds at a = 0.01? Be sure to state the hypotheses

and identify which of them is the claim.

V.

Green Life International advertises that those who join will lose an average of 10 pounds after the

First two weeks. The standard deviation is 2.8 pounds. A random sample of 50 people who joined the weight

loss program revealed a mean loss of 9. pounds.

Can we conclude that those joining Green Life will lose less than 10 pounds at a = 0.05? Be sure to state the hypotheses and identify which of them is the claim.