In: Statistics and Probability
Researchers measured the data speeds for a particular smartphone carrier at 50 airports. The highest speed measured was 71.7 Mbps. The complete list of 50 data speeds has a mean of x overbarequals18.12 Mbps and a standard deviation of sequals17.45 Mbps. a. What is the difference between carrier's highest data speed and the mean of all 50 data speeds? b. How many standard deviations is that [the difference found in part (a)]? c. Convert the carrier's highest data speed to a z score. d. If we consider data speeds that convert to z scores between minus2 and 2 to be neither significantly low nor significantly high, is the carrier's highest data speed significant?
The highest speed measured was 71.7 Mbps.
The complete list of 50 data speeds has a mean 
 = 18.12 Mbps and a standard deviation 
 = 17.45 Mbps.

The difference between carrier's highest data speed and the mean of all 50 data speeds = (71.7-18.12) Mbps = 53.58 Mbps

53.58/17.45 
 3.07 which implies that  the difference between
carrier's highest data speed and the mean of all 50 data speeds is
approximately 3.07 standard deviations

The z-score of the carrier's highest data speed =
(71.7-
)/
= (71.7-18.12)/17.45 
 3.07

If we consider data speeds that convert to z scores between -2 and 2 to be neither significantly low nor significantly high, the carrier's highest data speed is significant as it is approximately 3.07 and does not belong to the interval (-2,2).