ITPEC FE Subject A October 2025 Question 58
ITPEC FE Subject A October 2025 — Question 58 of 60
The OC curve plots percent defective (X-axis) vs probability of lot acceptance / success rate (Y-axis).
C = pass quantity (maximum allowed defective samples to accept the lot).
Key insight: larger C means a more lenient acceptance criterion → the curve shifts right (lot is accepted even at higher defect rates).
So left-to-right order of curves: C=0 → C=1 → C=2
This matches diagram (b).
Why not others:
- (a) — curves are ordered in reverse (C=0 is rightmost), which would mean stricter C accepts more defects — contradicts logic
- (c) — curves intersect near the origin; impossible since at 0% defects, acceptance probability = 100% for all C values
- (d) — same intersection problem as (c), plus wrong order
Key rule: Higher C = more lenient threshold = OC curve shifts right. At 0% defects, all curves must start at 100% acceptance (no intersection at origin).
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