Posted by **Anonymous** on Tuesday, February 23, 2010 at 11:39am.

College students average 7.8 hours of sleep per night with a standard deviation of 45 minutes. If the amount of sleep is normally distributed, what proportion of college students sleep for more than 9 hours?

- statistics -
**dongo**, Tuesday, February 23, 2010 at 11:51am
You know the value of expectation, 7.8h, you know the deviation, 0.75h and you know that the amount of students, sleeping more LESS than (or equal) 9 hours is:

/bigPhi((9h-7.8h)/0.75h)=

/bigPhi(1.6)

Hence the required probability to find such a student (sleeping MORE than 9 hours) is:

P=1-/bigPhi(1.6)

- statistics -
**PsyDAG**, Wednesday, February 24, 2010 at 12:57pm
Z = (x-μ)/SD

Z = (9-7.8)/.75 = 1.6

In table in the back of your stat text called something like "areas under normal distribution," look up Z score for smaller area to get proportion.

I hope this helps a little more.

- statistics -
**;loik**, Thursday, September 17, 2015 at 4:45am
;kjl

## Answer this Question

## Related Questions

- statistics - The typical amount of sleep per night for undergraduate college ...
- statistics - The number of hours that college students sleep on a week night is...
- Statistics - Suppose that hours of sleep per night for single adults between 30 ...
- statistics - based on a random sample of 640 college students, the mean amount ...
- statistics - researchers believe a new sleep on average 10 hours per night...
- Probability/Statistics - Using diaries for many weeks, a study on the lifestyles...
- Statistics - the average numbers of hours a cat sleep is approximately normally...
- statistics - (10 pts) Using diaries for many weeks, a study on the lifestyles of...
- Statistics (37) - According to the Sleep Foundation, the average night's sleep ...
- AP Statistics - A school psychologist reports that the mean number of hours the ...

More Related Questions