Problem $6-4($Algo$)$

Suppose that the Dallas School District wants to achieve Six Sigma quality levels of performance in

delivering students to school. It has established a $27-$minute window as an acceptable range within which

buses carrying students should arrive at school.

a$.$ What is the maximum allowable standard deviation of arrival times required in order to achieve this

standard of quality?

b$.$ If the school district achieves this standard, about how many times out of a million deliveries will a bus

deliver students either too early or too late?