A survey of mobile call interconnectivity indicates that the average time it takes to connect calls from one network to the other is 25 seconds.Assume the variable is approximately normally distributed and the standard deviation is 4.5 seconds.if 80 calls are randomly selected,approximately how many will be responded to
a.in less than 15 seconds.
b.between 20 and 24 seconds.
(under statistics, normal distribution )
Z = (score-mean)/SEm
SEm = SD/√n
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to each Z score. Multiply by 80.