MEM Operations Management 2 — Questions and Answers
Question 1: A factory produces 500 units per day with a defect rate of 4%. After implementing Six Sigma controls, the defect rate drops to 0.5%. What is the daily reduction in defective units?
- 17.5 units (Correct answer)
- 20 units
- 18 units
- 15 units
Correct answer: 17.5 units
Original defects = 500 × 0.04 = 20; new defects = 500 × 0.005 = 2.5; reduction = 17.5 units per day.
Question 2: Which scheduling rule minimizes the average number of jobs in the system when processing times are known?
- Shortest Processing Time (SPT) (Correct answer)
- First Come First Served (FCFS)
- Earliest Due Date (EDD)
- Critical Ratio (CR)
Correct answer: Shortest Processing Time (SPT)
SPT minimizes mean flow time and average work-in-process, thereby minimizing the average number of jobs in the system.
Question 3: In a Theory of Constraints analysis, the constraint operation processes 80 units/hour while all other stations process 100+ units/hour. Demand is 90 units/hour. What is the system throughput?
- 80 units/hour (Correct answer)
- 90 units/hour
- 100 units/hour
- 70 units/hour
Correct answer: 80 units/hour
System throughput is governed by the bottleneck (constraint), so output equals 80 units/hour regardless of demand.
Question 4: A company uses a periodic review inventory system with a review period of 2 weeks and a lead time of 1 week. Safety stock is calculated based on how many weeks of demand variability?
- 3 weeks (Correct answer)
- 2 weeks
- 1 week
- 4 weeks
Correct answer: 3 weeks
In a periodic review system, safety stock covers variability during the review period plus lead time (2 + 1 = 3 weeks).
Question 5: Which lean metric directly measures the ratio of value-added time to total lead time in a process?
- Process cycle efficiency (PCE) (Correct answer)
- Overall equipment effectiveness (OEE)
- Takt time
- Throughput ratio
Correct answer: Process cycle efficiency (PCE)
PCE = value-added time / total lead time, and a world-class PCE is typically above 25%.
Question 6: A project network has activities A(3d), B(5d), C(2d), D(4d) where A→C→D and A→B→D are the two paths. What is the critical path duration?
- 12 days (Correct answer)
- 9 days
- 10 days
- 11 days
Correct answer: 12 days
Path A→B→D = 3+5+4 = 12 days; Path A→C→D = 3+2+4 = 9 days; critical path is 12 days.
Question 7: In aggregate production planning, the 'chase strategy' specifically adjusts which resource to match demand fluctuations?
- Workforce levels (Correct answer)
- Inventory levels
- Machine capacity
- Supplier lead times
Correct answer: Workforce levels
The chase strategy matches production rate to demand by hiring and laying off workers, keeping inventory minimal.
MEM Operations Management 2
A factory produces 500 units per day with a defect rate of 4%.
After implementing Six Sigma controls, the defect rate drops to 0.5%.
What is the daily reduction in defective units?