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ICAR AIEEA-PG Statistical Quality Control & Reliability: practice questions

ICAR AIEEA-PG - Group 07 Statistical Sciences (Master's admission and PG scholarship) · India · National Testing Agency for ICAR

Original practice questions written to the published syllabus · not past papers
6worked here, free
28written to this exam in this subject
9syllabus units

What this subject covers

Monitoring and accepting quality: Shewhart charts for variables and attributes, CUSUM and EWMA charts, process capability, acceptance sampling plans with their OC, AOQ and ATI curves, and reliability models, applied to seed testing, food processing and input quality. The Agricultural Engineering track covers control charts briefly; this is the full subject.

In the exams: UPSC ISS Statistics III (heavy, reported); SSC CGL JSO (present); AICE-JRF Dairy Microbiology syllabus names 'statistical quality control' (present); light in AICE-JRF Ag Stat

Where the 28 questions fall

How our questions for ICAR AIEEA-PG spread across the units of Statistical Quality Control & Reliability. Difficulty: 14 easy, 14 medium, 0 hard.

Control charts for attributes: p, np, c and u charts5
Acceptance sampling by attributes: single, double and sequential plans5
OC, AOQ, AOQL, ASN and ATI curves5
Reliability: hazard rate, series and parallel systems, life testing4
Chance and assignable causes of variation3
Control charts for variables: X-bar, R and s charts3
CUSUM and EWMA charts1
Process capability indices1
Six Sigma and design for quality (introduction)1

6 practice questions, worked

Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.

1 · Control charts for variables: X-bar, R and s charts · medium

Subgroups of 5 bags give x̿ = 50.12 kg and R̄ = 0.40 kg; A₂ = 0.577. What are the X̄ chart limits?

  1. 49.72 to 50.52 kg
  2. 48.92 to 51.32 kg
  3. 49.889 to 50.351 kg
  4. 50.017 to 50.223 kg
Answer and working

C. 49.889 to 50.351 kg

x̿ ± A₂R̄ = 50.12 ± 0.231 = 49.889 to 50.351. A₂ already includes 1/√n, so dividing again is wrong.

Further reading: Montgomery, Introduction to Statistical Quality Control; Duncan, Quality Control and Industrial Statistics; Schilling and Neubauer, Acceptance Sampling in Quality Control

2 · Control charts for variables: X-bar, R and s charts · easy

For subgroups of 5 with R̄ = 0.40 kg, D₃ = 0 and D₄ = 2.114. What is the R chart upper limit?

  1. 0.846 kg
  2. 1.20 kg
  3. 0.231 kg
  4. 0.400 kg
Answer and working

A. 0.846 kg

UCL = D₄R̄ = 2.114 × 0.40 = 0.846; LCL = 0.

Further reading: Montgomery, Introduction to Statistical Quality Control; Duncan, Quality Control and Industrial Statistics; Schilling and Neubauer, Acceptance Sampling in Quality Control

3 · OC, AOQ, AOQL, ASN and ATI curves · easy

What is plotted on an OC curve?

  1. Defects against time
  2. Sample size against lot quality
  3. Outgoing quality against lot size
  4. P_a against lot quality
Answer and working

D. P_a against lot quality

The OC curve shows P_a(p) for each incoming fraction non-conforming.

Further reading: Montgomery, Introduction to Statistical Quality Control; Duncan, Quality Control and Industrial Statistics; Schilling and Neubauer, Acceptance Sampling in Quality Control

4 · Reliability: hazard rate, series and parallel systems, life testing · easy

Three components with reliabilities 0.95, 0.98 and 0.99 are in series. What is the system reliability?

  1. 0.922
  2. 0.973
  3. 0.950
  4. 0.999990
Answer and working

A. 0.922

Series: product = 0.922. 0.999999 is the parallel arrangement.

Further reading: Montgomery, Introduction to Statistical Quality Control; Duncan, Quality Control and Industrial Statistics; Schilling and Neubauer, Acceptance Sampling in Quality Control

5 · Reliability: hazard rate, series and parallel systems, life testing · medium

A pump with reliability 0.95 is duplicated in parallel. What is the reliability of the pump stage?

  1. 0.95
  2. 0.9975
  3. 0.9025
  4. 0.975
Answer and working

B. 0.9975

Parallel: 1 − (0.05)² = 0.9975; 0.9025 is the series value.

Further reading: Montgomery, Introduction to Statistical Quality Control; Duncan, Quality Control and Industrial Statistics; Schilling and Neubauer, Acceptance Sampling in Quality Control

6 · Reliability: hazard rate, series and parallel systems, life testing · medium

Twenty nozzles run 500 hours; four fail at 120, 250, 310 and 430 hours. Assuming exponential lives, what is the MLE of MTTF?

  1. 455.5 hours
  2. 277.5 hours
  3. 2500.0 hours
  4. 2277.5 hours
Answer and working

D. 2277.5 hours

Total time on test = 1,110 + 16 × 500 = 9,110 h; θ̂ = 9,110/4 = 2,277.5 h. Using only failed items' times gives 277.5 h.

Further reading: Montgomery, Introduction to Statistical Quality Control; Duncan, Quality Control and Industrial Statistics; Schilling and Neubauer, Acceptance Sampling in Quality Control

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Read the subject

Statistical Quality Control & ReliabilityThe full study manual, free ICAR AIEEA-PGFormat, sections and how it has changed

More ICAR AIEEA-PG practice

Statistical Methods for Agricultural SciencesAgriculture for StatisticiansDifferential Equations, Finite Differences & Numerical AnalysisPrinciples of Experimental Design & Basic DesignsProbability TheoryStatistical Inference II: Testing of Hypotheses & Sequential AnalysisProbability Distributions & Sampling DistributionsNonparametric & Rank-Based MethodsComputer Science Fundamentals: Architecture, Data Structures, Networks & Operating SystemsBioinformatics & Computational Biology

Statistical Quality Control & Reliability for other exams

State statistical services · IndiaIndian Statistical Service Examination · IndiaCUET-PG · IndiaGATE · IndiaIIT JAM · IndiaASRB Agricultural Research Service · IndiaASRB NET · IndiaIndian Statistical Institute admission tests · IndiaSSC Combined Graduate Level · India

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