# statistics

posted by .

ten randomly selected people were asked how long they slept at night. The mean time was 7.1 hours and the (sample) standard deviation was 0.78 hours. Find the 95% confidence interval of the mean time. Assume the variable is normally distributed.

• statistics -

95% confidence interval indicates that you have 5% outside the confidence interval and 2.5% on either side. This is an area of .025. You can use a calculator or a t-table to find the critical value.

Multiply that value times the standard deviation.

add this value to the mean and then subtract this value to the mean which will give you the confidence interval. Always write the confidence interval with the smaller value first.

## Similar Questions

1. ### statistics

A sample of 352 subscribers to Wired magazine shows the mean time spent using the Internet is 13.4 hours per week, with a sample standard deviation of 6.8 hours. Find the 95 percent confidence interval for the mean time Wired subscribers …
2. ### statistics

In a random sample of 50 babies 4 to 7 month old the average number of hours they slept per day turned out to be 14.2 hours with a standard deviation of 1.6 hours find and interpret a 90% confidence interval for the mean number of …
3. ### statistics

In a random sample of 50 babies 4 to 7 month old the average number of hours they slept per day turned out to be 14.2 hours with a standard deviation of 1.6 hours find and interpret a 90% confidence interval for the mean number of …
4. ### math

In a time-use study, 20 randomly selected managers were found to spend a mean of 2.40 hours each day on paperwork. The standard deviation of the 20 scores is 1.30 hours. Also, the sample data appear to have a bell-shaped distribution. …
5. ### statistics

In a time-use study, 20 randomly selected managers were found to spend a mean of 2.40 hours each day on paperwork. The standard deviation of the the 20 scores is 1.30. Also, the sample data appear to have a bell-shaped distribution. …
6. ### statistics

In a time-use study, 20 randomly selected managers were found to spend a mean of 2.40 hours each day on paperwork. The standard deviation of the the 20 scores is 1.30. Also, the sample data appear to have a bell-shaped distribution. …
7. ### statistics

1.A magazine reported that 6% of Americans read the news paper while driving. 100 drivers are selected at random, find the probability that exactly 25 of them say they read the newspaper while driving.(normal binomial formula to solve) …
8. ### AP Statistics

A school psychologist reports that the mean number of hours the students at this school sleep each night is 8 hours. The students believe the mean is not 8 hours. To find an estimate of the true mean, they select a random sample of …
9. ### statistics

A study of the amount of time it takes a mechanic to rebuild the transmission for a 1992 Chevrolet Cavalier shows that the mean is 8.4 hours and the standard deviation is 1.77 hours. Assume that a random sample of 40 mechanics is selected …
10. ### Statistics

A study of the amount of time it takes a mechanic to rebuild the transmission for a 1992 Cavalier shows that the mean is 4.5 hours and the standard deviation is .6 hours. If 42 mechanics are randomly selected, find the probability …

More Similar Questions