System data for the job shop of exercise 1 revealed that the average time spent by a job in the shop was approximately 4 working days. The model made the following predictions on seven independent replications, for average time spent in the shop:

3.70 4.21 4.35 4.13 3.83 4.32 4.05 a)- Is model output consistent with system behavior? Conduct a statistical test (use =0.01).

b)- If it is important to detect a difference of 0.5 day, what sample size is needed to have a power of 0.90? Interpret your results in terms of model validity or invalidity (use =0.01).