Question

Eva, the owner of eva's second time around wedding dresses, currently has five dresses to be altered, shown in the order in which they arrived: if eva uses the earliest due date first (edd) priority rule to schedule these jobs, what will be the average job tardiness?

Answer 1

The correct answer is 2.2 hours.

If Eva uses the earliest due date priority rule, the order of the dresses will be as follows: W (1 hour processing time, 1 hour due); Y (2 hrs processing time, 3 hrs due); V (3 hrs processing time, 5 hrs due); Z (5 hrs processing time, 7 hrs due); X (4 hrs processing time, 9 hrs due). 

It's easier to do the next step using real numbers. For example, if it's 11am now and W is due in 1 hour, then W is due at noon. If Y is due in 3 hours, then Y is due at 2pm, etc. Then, you need to use the processing time to see how long it will take to make the dresses. For example, since W takes one hour to process, it will be done by noon, its due date. 

This means that W and Y will be altered on time, V will be 1 hour late, Z will be 4 hours late, and X will be 6 hours late. To find the average tardiness, add these extra hours (1+4+6) = 11, and divide by the total number of dresses (even the ones that weren't late) 5: 11/5 = 2.2 hours.