Enclosure 2: Statistical Process Control: GATE / AMIE / PSU Question Bank
GATE / AMIE / PSU Question Bank
Statistical Process Control: A Step-by-Step Guide
🔹 Chapter 1: Introduction to SPC
MCQs
Statistical Process Control is primarily used to:
(A) Inspect finished products
(B) Improve process capability
(C) Replace quality planning
(D) Eliminate inspection
Ans: (B)
SPC is best described as a:
(A) Corrective technique
(B) Preventive technique
(C) Detection technique
(D) Sampling technique
Ans: (B)
Short Answer (1–2 marks)
Define Statistical Process Control.
State one objective of SPC.
🔹 Chapter 2: Statistical Foundations for SPC
MCQs
The measure most sensitive to extreme values is:
(A) Mean
(B) Median
(C) Mode
(D) Range
Ans: (A)
For a normal distribution, approximately what percentage of observations lie within ±3σ?
(A) 95%
(B) 97%
(C) 99.73%
(D) 100%
Ans: (C)
Numerical (GATE type)
If σ = 2 mm, find process spread.
Ans: 6σ = 12 mm
🔹 Chapter 3: Process Variation & Rational Subgrouping
MCQs
Variation inherent in a stable process is called:
(A) Assignable cause
(B) Special cause
(C) Common cause
(D) Measurement error
Ans: (C)
Adjusting a stable process increases variability. This phenomenon is called:
(A) Calibration
(B) Correction
(C) Rational control
(D) Tampering
Ans: (D)
Short Answer
Define rational subgrouping.
Why should common cause variation not be adjusted?
🔹 Chapter 4: Control Charts for Variables
MCQs
X̄–R chart is preferred when subgroup size is:
(A) 1
(B) 2–10
(C) >10
(D) Variable
Ans: (B)
Which chart must be interpreted first?
(A) X̄ chart
(B) R chart
(C) I chart
(D) p-chart
Ans: (B)
Numerical (PSU / GATE)
If X̄̄ = 50, R̄ = 4, A₂ = 0.577, find UCL of X̄-chart.
[
UCL = 50 + (0.577)(4) = 52.31
]
🔹 Chapter 5: Control Charts for Attributes
MCQs
A p-chart is used to monitor:
(A) Number of defects
(B) Defects per unit
(C) Fraction defective
(D) Process mean
Ans: (C)
Which chart assumes Poisson distribution?
(A) p-chart
(B) np-chart
(C) c-chart
(D) X̄ chart
Ans: (C)
Numerical
If average number of defects = 16, find UCL for c-chart.
[
UCL = 16 + 3\sqrt{16} = 28
]
🔹 Chapter 6: Process Capability Analysis
MCQs
Cp measures:
(A) Actual capability
(B) Process centering
(C) Potential capability
(D) Control stability
Ans: (C)
A capable process generally requires:
(A) Cp ≥ 0.8
(B) Cp ≥ 1.0
(C) Cp ≥ 1.33
(D) Cp ≥ 2.5
Ans: (C)
Numerical
USL = 120, LSL = 100, σ = 4.
Find Cp.
[
Cp = \frac{20}{24} = 0.83
]
🔹 Chapter 7: SPC-Based Process Improvement
MCQs
Reduction of common cause variation requires action by:
(A) Operator
(B) Inspector
(C) Supervisor
(D) Management
Ans: (D)
Short Answer
State the role of SPC in PDCA cycle.
List any two QC tools.
🔹 Chapter 8: Acceptance Sampling
MCQs
Producer’s risk is associated with:
(A) AQL
(B) LTPD
(C) AOQL
(D) OC curve slope
Ans: (A)
Acceptance sampling is:
(A) Process control technique
(B) Product control technique
(C) Process improvement tool
(D) Preventive method
Ans: (B)
Numerical
For n = 50, c = 1, if defectives = 2 →
❌ Reject the lot
🔹 Chapter 9: Measurement System Analysis
MCQs
Repeatability is related to:
(A) Operator variation
(B) Equipment variation
(C) Part variation
(D) Process variation
Ans: (B)
Acceptable %Gage R&R should be:
(A) ≤ 5%
(B) ≤ 10%
(C) ≤ 30%
(D) ≥ 50%
Ans: (B)
Short Answer
Define reproducibility.
What is NDC?
🔹 Chapter 10: SPC Implementation & Trends
MCQs
SPC should be used for:
(A) Employee evaluation
(B) Process monitoring
(C) Punishment system
(D) Incentive decisions
Ans: (B)
Digital SPC is associated with:
(A) Manual charts
(B) Offline inspection
(C) Real-time data analysis
(D) Sampling inspection
Ans: (C)
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