12.4

A scientific study was conducted to determine the hours of sleep that college students get per night. The study surveyed 32 college students and obtained the following data:

8.2, 7.3, 6.9, 7.9, 7.5, 7.3, 7.8, 7.2, 6.9, 7.6, 7.4, 7.5, 7.8, 7.6, 6.9, 7.3, 8, 6.9, 7.4, 7.1, 6.9, 7.2, 7.6, 7.6, 6.7, 7, 7.5, 8.4, 8.2, 7.7, 6.3, 6.8

Assuming the population standard deviation is =0.45=0.45, construct a 85% confidence interval for the average hours of sleep per night that college students get.

x=____

2=_____

z2=____

Margin of Error: E=_____

We are 85% confident that college students get an average of between ____hours and _____hours of sleep per night.

12.5

A psychiatrist is interested in finding a 90% confidence interval for the tics per hour exhibited by children with Tourette syndrome. The data below show the tics in an observed hour for 11 randomly selected children with Tourette syndrome. Round answers to 3 decimal places where possible.

11 12 0 7 11 12 12 11 6 8 8

a. To compute the confidence interval use a ?

z

or

t distribution.______

b. With 90% confidence the population mean number of tics per hour that children with Tourette syndrome exhibit is between ______and ______.

c. If many groups of 11 randomly selected children with Tourette syndrome are observed, then a different confidence interval would be produced from each group. About _______ percent of these confidence intervals will contain the true population mean number of tics per hour and about _______percent will not contain the true population mean number of tics per hour.

12.6

If n=20n=20, xx=46, and s=6s=6, construct a confidence interval at a 98% confidence level. Give your answers to one decimal place.

______< < _____

12.7

Express the confidence interval 9%

_____% %______

12.9

A psychologist is interested in constructing a 90% confidence interval for the proportion of people who accept the theory that a person's spirit is no more than the complicated network of neurons in the brain. 62 of the 774 randomly selected people who were surveyed agreed with this theory. Round answers to 4 decimal places where possible.

a. With 90% confidence the proportion of all people who accept the theory that a person's spirit is no more than the complicated network of neurons in the brain is between _____and_____.

b. If many groups of 774 randomly selected people are surveyed, then a different confidence interval would be produced from each group. About _______percent of these confidence intervals will contain the true population proportion of all people who accept the theory that a person's spirit is no more than the complicated network of neurons in the brain and about _______percent will not contain the true population proportion.