What fraction of the days in 20032004 failed to meet the tar

What fraction of the days in 2003-2004 failed to meet the targed hold time of 110 seconds? Given that the daily average hold time was normally distributed with a mean of 99.67 and a standard deviation of 24.24, what fraction of days where the call center failed to meet the targeted hold time of 110 seconds would you expect?

Solution

P(X<110) = P((X-mean)/s <(110-99.67)/24.24)

=P(Z<0.43) =0.6664 (from standard normal table)