MNO2602 Assignment 4
(COMPLETE ANSWERS)
Semester 1 2025 - DUE
May 2025
For assistance contact
Email:
, MNO2602 Assignment 4 (Semester 1, 2025)
Total Marks: 40
Question 1 [16 marks]
1.1 Distinguish between random variation and nonrandom variation in a process. (6)
- Random variation (common cause variation):
• Inherent in a process.
• Caused by unknown factors that are always present.
• Affects all parts of the process.
• Small, consistent variation.
• Cannot be easily eliminated.
- Nonrandom variation (assignable cause variation):
• Caused by specific, identifiable factors.
• Usually a result of a change in materials, machines, or methods.
• Larger and unpredictable.
• Can and should be investigated and eliminated.
1.2 Discuss the different nonrandom signals that can occur when using a process control chart
to analyse a process. (5)
Nonrandom signals include:
1. A single point outside control limits.
2. A run of seven or more points on one side of the mean.
3. A trend of seven or more points continuously increasing or decreasing.
4. Cycles or patterns (e.g., zigzag patterns).
5. Sudden shift in process level (change in the average).
1.3 Explain the various types of attributes. (5)
Attribute data is qualitative and involves:
1. Defective/Non-defective: Whether a product meets specifications.
2. Number of Defects: Count of problems per unit.
3. Pass/Fail: Binary outcome.
4. Go/No-go gauges: Accept/reject results.
5. Categorical classification: Types of defects (e.g., scratch, dent, discoloration).
Question 2 [10 marks]
2.1 Calculate the control limits for an X̄ chart, with the range as measure of dispersion. (5)
Sample size (n) = 3; A₂ = 1.023
(COMPLETE ANSWERS)
Semester 1 2025 - DUE
May 2025
For assistance contact
Email:
, MNO2602 Assignment 4 (Semester 1, 2025)
Total Marks: 40
Question 1 [16 marks]
1.1 Distinguish between random variation and nonrandom variation in a process. (6)
- Random variation (common cause variation):
• Inherent in a process.
• Caused by unknown factors that are always present.
• Affects all parts of the process.
• Small, consistent variation.
• Cannot be easily eliminated.
- Nonrandom variation (assignable cause variation):
• Caused by specific, identifiable factors.
• Usually a result of a change in materials, machines, or methods.
• Larger and unpredictable.
• Can and should be investigated and eliminated.
1.2 Discuss the different nonrandom signals that can occur when using a process control chart
to analyse a process. (5)
Nonrandom signals include:
1. A single point outside control limits.
2. A run of seven or more points on one side of the mean.
3. A trend of seven or more points continuously increasing or decreasing.
4. Cycles or patterns (e.g., zigzag patterns).
5. Sudden shift in process level (change in the average).
1.3 Explain the various types of attributes. (5)
Attribute data is qualitative and involves:
1. Defective/Non-defective: Whether a product meets specifications.
2. Number of Defects: Count of problems per unit.
3. Pass/Fail: Binary outcome.
4. Go/No-go gauges: Accept/reject results.
5. Categorical classification: Types of defects (e.g., scratch, dent, discoloration).
Question 2 [10 marks]
2.1 Calculate the control limits for an X̄ chart, with the range as measure of dispersion. (5)
Sample size (n) = 3; A₂ = 1.023
