statistical monitoring of processes to detect special causes of … · control charts • a key...
TRANSCRIPT
![Page 1: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/1.jpg)
Statistical Process Control
Statistical Monitoring of Processes to Detect Special Causes of Variation
![Page 2: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/2.jpg)
Lecture Outline
• Basics of Statistical Process Control • Control Charts • Control Charts for Attributes • Control Charts for Variables • Control Chart Patterns • SPC with Excel • Process Capability
![Page 3: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/3.jpg)
Statistical QA Approaches
Statistical process control (SPC) • Monitors production process to prevent poor quality Acceptance sampling • Inspects random sample of product to determine if a lot is acceptable Design of Experiments
![Page 4: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/4.jpg)
Statistical Quality Assurance
Purpose: Assure that processes are performing in an acceptable manner Methodology: Monitor process output using statistical techniques If results are acceptable, no further action is required Unacceptable results call for corrective action Acceptance Sampling: Quality assurance that relies primarily on inspection before and after production Statistical Process Control (SPC): Quality control efforts that occur during production
![Page 5: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/5.jpg)
What is SPC?
A simple, yet powerful, collection of tools for graphically analyzing process data Has one primary purpose: To tell you when you have a problem Invented by Walter Shewhart at AT&T to minimize process tampering Important because unnecessary process changes increase instability and increase the error rate SPC will identify when a problem (or special cause variation) occurs
![Page 6: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/6.jpg)
Basics of Statistical Process Control
Statistical Process Control (SPC) - Monitoring production process
to detect and prevent poor quality
Sample - Subset of items produced to use
for inspection
Control Charts - Process is within statistical control charts
![Page 7: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/7.jpg)
![Page 8: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/8.jpg)
Production Data always has some Variability
![Page 9: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/9.jpg)
Chance and Assignable Causes of Quality Variation
![Page 10: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/10.jpg)
Accuracy and Precision
![Page 11: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/11.jpg)
Normal Distribution – Shaft Diameter (What is this plot of data telling us?)
![Page 12: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/12.jpg)
Variability
Random • Common causes • Inherent in a process • Can be eliminated only
through improvements in the system
Non-Random • Special causes • Due to identifiable factors • Can be modified through
operator or management action
![Page 13: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/13.jpg)
Plot of Sample Averages
![Page 14: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/14.jpg)
Control Charts
• A key tool in SPC • Graph establishing process control limits • Charts for variables Mean (X-bar), Range (R), EWMA, CUSM • Charts for attributes p, np, and c
![Page 15: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/15.jpg)
The Shewhart Control Chart
• A time-ordered plot of sample statistics • When chart is within control limits Only random or common causes present We leave the process alone • Plot of each point is the test of hypothesis: H0 : Process is “in control” vs. H1 : Process is out of control and requires investigation
![Page 16: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/16.jpg)
How Does the Chart Work?
![Page 17: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/17.jpg)
Relationship between “X” (process) and “X-bar” (the control chart)
![Page 18: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/18.jpg)
A Process is “In Control” if
• No sample points are outside limits • Most points near process average • About equal number of points above & below centerline • Points appear randomly distributed • A process “in control” is supposed to be under the influence of
random causes only
![Page 19: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/19.jpg)
The Signal from a Control Chart
![Page 20: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/20.jpg)
Potential Reasons for Variation
![Page 21: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/21.jpg)
Charts may signal incorrectly!
![Page 22: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/22.jpg)
Two Types of Process Data
![Page 23: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/23.jpg)
Types of Control Charts
• Basic Types Most typical three: X-Bar and R p chart c chart Depend Upon Data Type: Variables Attribute • Advanced Types: CUSUM, EWMA, Mulitvariate • Recall that plotting points on a control chart is the repeated application of
Hypothesis Testing
![Page 24: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/24.jpg)
SPC Applied To Services
• Nature of defect is different in services
• Service defect is a failure to meet customer requirement
• Monitor times, customer satisfaction
![Page 25: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/25.jpg)
Applying SPC to Service (cont.)
• Hospitals Timeliness and quickness of care, staff responses to requests, accuracy of lab tests, cleanliness, courtesy, accuracy of paperwork, speed of admittance and checkouts • Grocery Stores Waiting time to check out, frequency of out-of-stock items, quality of food items, cleanliness, customer complaints, checkout register errors • Airlines Flight delays, lost luggage and luggage handling, waiting time at ticket counters and check-in, agent and flight attendant courtesy, accurate flight information, passenger cabin cleanliness and maintenance
![Page 26: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/26.jpg)
Applying SPC to Service (cont.)
• Fast-Food Restaurants Waiting time for service, customer complaints, cleanliness, food quality, order accuracy, employee courtesy • Catalogue-Order Companies Order accuracy, operator knowledge and courtesy, packaging, delivery time, phone order waiting time • Insurance Companies Billing accuracy, timeliness of claims processing, agent availability and response time
![Page 27: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/27.jpg)
Service SPC Examples
• Hospitals Timeliness, responsiveness, accuracy • Grocery Stores Check-out time, stocking, cleanliness • Airlines Luggage handling, waiting times, courtesy • Fast-food Restaurants Waiting times, food quality, cleanliness • Banks Daily balance errors, # of customers served, transactions completed, courtesy
![Page 28: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/28.jpg)
Types of Shewhart Control Charts
![Page 29: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/29.jpg)
Control Charts for Variables
![Page 30: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/30.jpg)
X-bar Chart helps control Accuracy
![Page 31: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/31.jpg)
Normal Distribution
![Page 32: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/32.jpg)
![Page 33: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/33.jpg)
![Page 34: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/34.jpg)
![Page 35: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/35.jpg)
![Page 36: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/36.jpg)
![Page 37: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/37.jpg)
![Page 38: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/38.jpg)
![Page 39: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/39.jpg)
![Page 40: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/40.jpg)
![Page 41: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/41.jpg)
![Page 42: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/42.jpg)
![Page 43: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/43.jpg)
![Page 44: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/44.jpg)
![Page 45: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/45.jpg)
![Page 46: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/46.jpg)
![Page 47: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/47.jpg)
![Page 48: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/48.jpg)
![Page 49: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/49.jpg)
![Page 50: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/50.jpg)
![Page 51: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/51.jpg)
![Page 52: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/52.jpg)
![Page 53: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/53.jpg)
![Page 54: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/54.jpg)
![Page 55: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/55.jpg)
![Page 56: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/56.jpg)
![Page 57: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/57.jpg)
![Page 58: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/58.jpg)
![Page 59: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/59.jpg)
![Page 60: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/60.jpg)
![Page 61: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/61.jpg)
![Page 62: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/62.jpg)
![Page 63: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/63.jpg)
![Page 64: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/64.jpg)
![Page 65: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/65.jpg)
Monitoring the Process by Control Charts
We look now for abnormal patterns on the charts
![Page 66: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/66.jpg)
Using x-bar and R-Charts Together
• Process average and process variability must be in control.
• It is possible for samples to have very narrow ranges, but their averages are beyond control limits.
• It is possible for sample averages to be in control, but ranges might be very large.
![Page 67: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/67.jpg)
Performance Variation Patterns
![Page 68: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/68.jpg)
Abnormal Control Chart Patterns
![Page 69: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/69.jpg)
Abnormal Control Chart Patterns
![Page 70: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/70.jpg)
Zones for Non-Random Pattern Tests
![Page 71: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/71.jpg)
Abnormal Control Chart Patterns
1. 8 consecutive points on one side of the centre line
2. 8 consecutive points up or down across zones. 3. 14 points alternating up or down 4. 2 out of 3 consecutive points in zone A but still
inside the control limits 5. 4 out of 5 consecutive points in zone A or B
![Page 72: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/72.jpg)
Reaction Plan to use when process is out of control
![Page 73: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/73.jpg)
Sample Size
Attribute charts require larger sample sizes: 50 to 100 parts in a sample Variable charts require smaller samples: 2 to 10 parts in a sample
![Page 74: Statistical Monitoring of Processes to Detect Special Causes of … · Control Charts • A key tool in SPC • Graph establishing process control limits • Charts for variables](https://reader034.vdocuments.mx/reader034/viewer/2022042404/5f1a14985eab7b22300521f5/html5/thumbnails/74.jpg)
From Control to Improvement