Upload
griselda-parsons
View
217
Download
0
Tags:
Embed Size (px)
Citation preview
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 1
Chapter 12
Statistically-Based Quality Improvement
for Attributes
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 2
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Chapter 12
Types of attributesGeneric process for developing attribute chartsUnderstanding attribute chartsChoosing the right attributes chartReliability models
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 3
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Types of Attributes
Types of Attributes
StructuralSensoryPerformanceTemporalEthical
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 4
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Generic process for developing attribute charts
1. Identify Critical Operations
2. Identify critical product characteristics
3. Determine whether the product characteristics is a variable or an attribute
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 5
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Generic process for developing attribute charts
4. Select the appropriate process chart
5. Establish control limits
6. Update the limits when changes have been made to the process
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 6
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
Attribute Charts deal with binomial and Poisson processes, not measurements
Think in terms of defects and defectives rather than diameters and widths
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 7
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
A defect is an irregularity or problem with a larger unit
The larger unit may contain many defects Defects are countable
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 8
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
A defective is a unit that, as a whole, is not acceptable or does not meet performance requirements
Defectives are monitored p and np charts
Defects are monitored using c and u charts
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 9
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
A p chart is a process chart that is used to graph the proportion of items in a sample that are defective
Effective to determine when there has been a shift in the proportion defectives for a particular product or service
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 10
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
p chart applications include: Late deliveries Incomplete orders Calls not getting dial tones Accounting transaction errors Clerical errors on written forms Parts that do not mate properly
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 11
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
p charts for example 12-1
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 12
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
Example 12-1 using excel
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 13
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
The np chart is a graph of the number of defectives in a subgroup
The np chart requires the sample size of each subgroup be the same each time a sample is drawn
The uses for the np chart are essentially the same as the p chart
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 14
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
np charts for example 12-2
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 15
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
Example 12-2 using excel
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 16
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
The c chart is a graph of the number of defects per unit
The units must be of the same metric .. size, height, length, volume …
The c chart is used to detect nonrandom events in the life of a production process
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 17
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
c chart
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 18
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
The u chart is a graph of the average number of defects per unit.
The units can be of different Sizes, height, length, volume …
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 19
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
u chart
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 20
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Understanding Attribute Charts
c and u charts using excel
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 21
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Choosing the Right Attributes Chart
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 22
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Reliability Models
Bathtub shaped function The vertical axis is the failure rate The horizontal axis is time Shows products are
more likely to fail either
early or late in their
useful lifetimes
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 23
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Reliability Models
Series reliability Components are in a series if the
performance of the entire system depends on all the components functioning properly
The components need not be physically wired sequentially
All parts must function for the system to function
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 24
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Reliability Models
Parallel reliability High reliability systems often require
extremely require high component reliability
When it is impossible an alternative is to use a backup system
Another word for backup is redundant or parallel
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 25
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Reliability Models
Measuring reliability
Failure rate = l = number of failures>(units tested * number of hours tested)
Mean Time to failure =
Mean Time Between Failures = total operating hours>number of failures
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 26
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Reliability Models
System Availability
System availability = MTBF>(MTBF + MTTR)
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 27
Strategic Quality PlanningStatistically-Based Quality Improvement for Attributes Summary
Types of attributesGeneric process for developing attribute chartsUnderstanding attribute chartsChoosing the right attributes chartReliability models
Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall.12- 28
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or
otherwise, without the prior written permission of the publisher. Printed in the United States of America.