Q1.(i) A manufacturing firm has previously sequenced its jobs using the "Shortest Operation Time" (SOT) rule. This has resulted in poor delivery performance with many jobs being delivered late. They have now changed to the "Earliest Due Date" (EDD) rule in an attempt to improve their service to customers. Two samples of data, one using SOT and one using EDD are shown below:
(a) Use a SIMPLE test to check if the data can be regarded as "reasonably" Normal.
(b) Has the delivery performance improved since the new (EDD) rule was introduced? Explain your answer.
Note: "Negative Lateness" means the job was Early.
(ii) Fluorescent light tubes used by a firm have a target life of 1600 hours. However, accumulated data shows a mean time to failure of 1570 hours. What proportion of the tubes could be expected to achieve the target life? (Explain your choice of model.).