Statistics
posted by Pat .
How large a sample of U.S. adults is needed in order to estimate U with a 95% confidence interval of length 1.2 hours?

Statistics 
MathGuru
I assume this was part of your previous post:
A study was conducted in order to estimate u, the mean number of weekly hours that U.S. adults use computers at home. Suppose a random sample of 81 U.S. adults give a mean weekly computer usage time of 8.5 hours and that from prior studies , the population standard deviation is assumed to be 3.6 hours.
If so, use this formula:
Margin of error = zvalue * sd/√n
With your data:
1.2 = 1.96 * 3.6/√n
Solve for n. 
Statistics 
jas
136
Respond to this Question
Similar Questions

Probability and Statistics
The major would like to estimate the mean number of automobile crashes per day at the intersection of 2 highways. A random sample of 40 days worth of data had a mean of 4.3 crashes and a standard deviation of 0.9. How large of a sample … 
Elementary Statistics
1) Construct a confidence interval of the population proportion at the given level of confidence. x=60,n=300, 99% confidence. The 99% confidence interval is (_,_) 2) A researcher wishes to estimate the proportion of adults who have … 
statistics
how large a sample size is needed for 2 sided 95% confidence interval to have a length of 2 weeks when mean is 3.6 
statistics
A film alliance used a random sample of 50 U.S. citizens to estimate that the typical American spent 78 hours watching videos and DVDs last year. The standard deviation of this sample was 9 hours. (a) Develop a 95 percent confidence … 
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 … 
Statistics
Use the sample data and confidence level to construct the confidence interval estimate of the population proportion p. n=500, x=350, 90% confidence ? 
statistics
How large a sample would be needed to form a 90% confidence interval for the mean nicotine content of a brand of cigarettes if the nicotine content has a normal distribution with sigma equal to 8.5 mg and the width of the interval … 
statistics
A data set includes body temperatures of healthy adult humans for which x= 98.2 and s=0.64 F. Complete parts a) and b) below a) what is the best point estimate of the mean body temperature of all healthy humans? 
Statistics 101
A researcher plans to use a random sample of n= 500 families to estimate the mean monthly family incomefor a large population. a 99% confidence interval based on the sample would be _________ than 90% confidence interval. 
Introduction to statistics
A researcher would like to estimate the population proportion of adults living in a certain town who have at least a high school education. No information is available about its value. How large a sample size is needed to estimate …