Question

In a study of wait times at an amusement park, the most popular roller coaster has a mean wait time of 17.4 minutes with a standard deviation of 5.2 minutes. If 30 days are randomly selected, find the probability that the mean wait time is greater than 20 minutes.
0.0031
0.3207
0.1023
0.9987

Answer 1

we can use TI 83/84

normalcdf ( 20, 1E99, 17.4, 5.2/sqrt(30))

Answer 2

this is actually a mean of a sample , so we have to change the standard deviation, divide by the square root of the sample size . (this is also called standard error )

Answer 3

= .003085... ~ .0031