Answer
a) Didn't change.
b) The variation lowered.
c) Satisfaction increased
d) The single line is preferable.
Work Step by Step
a) From the data, we can see that the mean waiting time did not change, because the means of the two data sets are the same.
b) The problem says that the standard deviation changed from $1.8$ to $0.5$, hence the deviation lowered.
c) Satisfaction increased, because the waiting time was more consistent. After all, even if the average does not change, people are more satisfied when the time it takes is more consistent.
d) The single line is preferable, because it improves customer satisfaction.
