A study found that 8-to 12-year olds spend an average of $18.50 per trip to mall. If a sample of 49 children was used, find the 99% confidence inteval of the mean. Assume the standard deviation is $1.50.
The standard deviation from the mean for the average of 49 students will be 1.50/sqrt49 = $0.214. The 99% confidence inverval is $17.95 to $19.05
I used the normal distribtion tool at
http://psych.colorado.edu/~mcclella/java/normal/accurateNormal.html