Industrial Engineering and Management
What you must command
Work study (method study and work measurement), time and motion study, productivity, forecasting, inventory control (EOQ, reorder level, ABC analysis), production planning and control, quality control (control charts, sampling), plant layout, CPM/PERT project networks, and principles of management and organisation.
Traps that appear in questions
- EOQ: Q = √(2DS/H), where D is annual demand, S ordering cost, H holding cost per unit per year. Mixing monthly and annual figures is the classic error.
- Productivity: output/input; distinguish partial from total factor productivity.
- CPM vs. PERT: CPM is deterministic (activity-on-arrow), PERT probabilistic with three time estimates; expected time = (O + 4M + P)/6.
- Control charts: X-bar chart monitors the mean, R chart the range; UCL/LCL at ±3σ.
- ABC analysis: A items are few but high value; control them tightly.
- Float/slack: critical path has zero float; delaying it delays the project.
Worked rule of thumb
EOQ example: annual demand D = 12 000 units, ordering cost S = ₹500, holding cost H = ₹30 per unit per year. Q = √(2 × 12 000 × 500/30) = √(400 000) = 632 units. Ordering frequency ≈ 12 000/632 ≈ 19 orders per year. Sanity check: at EOQ, ordering cost equals holding cost - a quick verification.
For PERT, if optimistic = 4, most likely = 6, pessimistic = 14 days, expected time = (4 + 24 + 14)/6 = 7 days. Always convert all inputs to the same unit before averaging.