Suppose an automobile association reports that the average time it takes to respond to an emergency call is 25 minutes. Assume the variable is approximately normally distributed and the standard deviation is 4.5 minutes. If 104 calls are randomly selected, approximately how many will be responded to in less than 22 minutes?
Statistics - PsyDAG, Saturday, February 4, 2012 at 4:57am
Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score. Multiply that by 104.