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Chapter 9 1Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 2Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

8.1 The Cumulative Sum Control Chart

Chapter 9 3Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 4Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

The Cumulative Sum Control Chart

Chapter 9 5Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

The Tabular Cusum

Chapter 9 6Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 7Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 8Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 9Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Cusum Status Chart (Figure 9.3a)

Chapter 9 10Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

MINITAB Version of Cusum Status Chart

Minitab calculates the lower Cusum this way

Chapter 9 11Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 12Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Recommendations for Cusum Design

Chapter 9 13Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 14Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

The Standardized Cusum

Chapter 9 15Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Improving Cusum Performance for Large Shifts: The

Combined Shewhart-Cusum Scheme

Chapter 9 16Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

The Fast Initial Response (FIR) Cusum

K = 3, H = 12, headstart = H/2 = 6

Chapter 9 17Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

H = 12 implies that the cusum signals at sample 3

Without the headstart, it would not signal until sample 6

Chapter 9 18Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 19Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

More on Cusums

• Cusums are often used to determine if a process has

shifted off a specified target because it is easy to

calculate the required adjustment

• One-sided cusums are often useful

• Cusums can also be used to monitor variability

• Cusums are available for other sample statistics

(ranges, standard deviations, counts, proportions)

• Rational subgroups and cusums

Chapter 9 20Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 21Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

The Cusum V-Mask

Chapter 9 22Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 23Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 24Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 25Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 26Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 27Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

9.2 The Exponentially Weighted Moving

Average Control Chart

The EWMA is

Chapter 9 28Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 29Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Steady-state

control limits

Chapter 9 30Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 31Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 32Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 33Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Design of the EWMA

Chapter 9 34Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 35Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 36Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Robustness of EWMA to

Non-normal Process Data

Chapter 9 37Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 38Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 39Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Extensions of the EWMA

• Fast initial response feature

• Monitoring variability

• Monitoring count data

• The EWMA as a predictor of process level

Chapter 9 40Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

9.3 The Moving Average Control Chart

Chapter 9 41Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

Chapter 9 42Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright (c) 2013 John Wiley & Sons, Inc.

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