Quality Control PowerPoint Presentation, PPT - DocSlides

Download

  • Likes: 13
  • Views: 22
  • marina-yarberry

Description

Quality Control PowerPoint Presentation, PPT - DocSlides - Chapter 10. MIS 373: Basic Operations Management. Additional content from Jeff . Heyl. Learning Objectives. After this lecture, students will be able to . Explain the need for quality control. .. List and briefly explain the elements of the control process.

Download this presentation

Quality Control PowerPoint Presentation, PPT - DocSlides

Click below link (As may be) to download this presentation.

Download Note - The PPT/PDF document "Quality Control PowerPoint Presentation,..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.

Quality Control PowerPoint Presentation, PPT - DocSlides

    Slide1

    Quality Control

    Chapter 10

    MIS 373: Basic Operations Management

    Additional content from Jeff Heyl

    Slide2

    Learning Objectives

    After this lecture, students will be able to Explain the need for quality control.List and briefly explain the elements of the control process.Explain Type I and Type II errorsExplain how control charts are used to monitor a process and the concepts that underlie their use.

    MIS 373: Basic Operations Management

    2

    Slide3

    Background Knowledge

    How many of you have had at least one statistics course?

    Normal distribution?

    Standard deviation?

    Z score?

    Slide4

    Motivations

    Making Beer Better With Quality and Statistics

    http://

    videos.asq.org/making-beer-better-with-quality-and-statistics

    Quality for Life: Psychic Pizza

    http://

    videos.asq.org/quality-for-life-psychic-pizza

    Slide5

    What is Quality Control?

    Quality ControlA process that evaluates output relative to a standard and takes corrective action when output doesn’t meet standardsIf results are acceptable no further action is requiredUnacceptable results call for correction actionPhases of Quality Assurance

    MIS 373: Basic Operations Management

    5

    Slide6

    Inspection

    InspectionAn appraisal activity that compares goods or services to a standardInspection issues:What to inspectCount number of times defect occursMeasure the value of a characteristicHow much to inspect and how oftenAt what points in the process to inspectRaw materials and purchased partsFinished productsBefore a costly operationBefore an irreversible processCostly, possibly destructive, and disruptive – non value-addingFull inspection vs. Sampling

    MIS 373: Basic Operations Management

    6

    Slide7

    How Much to Inspect

    MIS 373: Basic Operations Management

    7

    Slide8

    How Much to Inspect

    MIS 373: Basic Operations Management

    8

    1 defect in 1 thousand unites

    1 defect in 1 million unites

    1 defect in 1 billion unites

    Trying to catch:

    Slide9

    Centralized vs. On-Site Inspection

    Effects on cost and level of disruption are a major issue in selecting centralized vs. on-site inspectionCentralizedSpecialized tests that may best be completed in a labMore specialized testing equipmentMore favorable testing environmentOn-SiteQuicker decisions are renderedAvoid introduction of extraneous factorsQuality at the source

    MIS 373: Basic Operations Management

    9

    Slide10

    Statistical Process Control (SPC)

    Quality control seeksQuality of ConformanceA product or service conforms to specificationsA tool used to help in this process:SPC Statistical evaluation of the output of a processHelps us to decide if a process is “in control” or if corrective action is needed“In control” means that the variation in the provided products/services is tolerable

    MIS 373: Basic Operations Management

    10

    Slide11

    Process Variability

    Two basic questions: concerning variability:Issue of Process ControlAre the variations random? If nonrandom variation is present, the process is said to be unstable. Variations randomly distributed within control limitsIssue of Process CapabilityGiven a stable process, is the inherent variability of the process within a range that conforms to performance criteria? The control limits satisfy the design specification

    MIS 373: Basic Operations Management

    11

    Slide12

    Variation

    VariationRandom (common cause) variation: Natural variation in the output of a process, created by countless minor factorsAssignable (special cause) variation: A variation whose cause can be identified. A nonrandom variationIllustration: M&M’sSizeColor

    MIS 373: Basic Operations Management

    12

    Slide13

    Variation

    Common causeInappropriate proceduresPoor designPoor maintenance of machinesLack of clearly defined standard operating proceduresPoor working conditions, e.g. lighting, noise, dirt, temperature, ventilationSubstandard raw materialsMeasurement errorQuality control errorVibration in industrial processesAmbient temperature and humidityNormal wear and tearVariability in settings

    Special causePoor adjustment of equipmentOperator falls asleepFaulty controllersMachine malfunctionFall of groundComputer crashPoor batch of raw materialPower surgesHigh healthcare demand from elderly peopleBroken partAbnormal traffic (click fraud) on web adsExtremely long lab testing turnover time due to switching to a new computer systemOperator absent

    MIS 373: Basic Operations Management

    13

    Slide14

    Sampling and Sample Distribution

    SPC involves periodically taking samples of process output and computing sample statistics:Sample meansThe number of occurrences of some outcomeSample statistics are used to judge the randomness of process variation

    MIS 373: Basic Operations Management

    14

    Slide15

    Sampling and Sample Distribution

    Sampling DistributionA theoretical distribution that describes the random variability of sample statisticsThe normal distribution is commonly used for this purposeCentral Limit TheoremThe distribution of sample averages tends to be normal regardless of the shape of the underlying process distribution

    MIS 373: Basic Operations Management

    15

    Slide16

    Demo

    Use simulation to test the Central

    Limit

    Theorem

    Slide17

    The Normal Distribution

    MIS 373: Basic Operations Management

    17

    Slide18

    Control Process

    Sampling and corrective action are only a part of the control processSteps required for effective control:Define: What is to be controlled?Measure: How will measurement be accomplished?Compare: There must be a standard of comparisonEvaluate: Establish a definition of out of controlCorrect: Uncover the cause of nonrandom variability and fix itMonitor results: Verify that the problem has been eliminated

    MIS 373: Basic Operations Management

    18

    Slide19

    Control Charts: The Voice of the Process

    Control ChartA time ordered plot of representative sample statistics obtained from an ongoing process (e.g. sample means), used to distinguish between random and nonrandom variabilityControl limitsThe dividing lines between random and nonrandom deviations from the mean of the distributionUpper and lower control limits define the range of acceptable variationUpper control limit = UCL = mean + zσLower control limit = LCL = mean + zσ

    MIS 373: Basic Operations Management

    19

    Slide20

    UCL

    LCL

    Mean

    Control

    Chart Example

    Each point on the control chart represents a sample of

    n

    observations

    MIS 373: Basic Operations Management

    Sample number

    | | | | | | | | | | | |

    1 2 3 4 5 6 7 8 9 10 11 12

    Variation due to assignable causes

    Variation due to assignable causes

    Variation due to natural causes

    Out of control

    Out of control

    20

    Slide21

    Errors

    Type I errorNarrow control limitsConcluding a process is not in control when it actually is.Manufacturer’s RiskType II errorWide control limitsConcluding a process is in control when it is not.Consumer’s Risk

    MIS 373: Basic Operations Management

    Alarm

    No Alarm

    Process

    In-Control

    Process

    Out-of-Control

    Type I

    Type II

    n

    o-error

    no-error

    21

    Slide22

    Errors Illustration

    Q: I always get confused about Type I and II errors. Can you show me something to help me remember the difference?

    Source:

    Effect

    Size FAQs

     

    by

    Paul Ellis

    Slide23

    Control Charts

    MIS 373: Basic Operations Management

    Every process displays variation in performance: normal or abnormalControl charts monitor process to identify abnormal variation Do not tamper with a process that is “in control” with normal variation Correct an “out of control” process with abnormal variationControl charts may cause false alarms – too narrow - (or missed signals – too wide) by mistaking normal (abnormal) variation for abnormal (normal) variation

    Out of Control In Control Improved

    LCL

    

    UCL

    23

    Slide24

    Control Charts

    Data that are measured“x-bar” charts (Mean)Used to monitor the central tendency of a process.R charts (Range)Used to monitor the process dispersion

    MIS 373: Basic Operations Management

    24

    Slide25

    x-bar (sample average) chart Control Limits

    MIS 373: Basic Operations Management

    )k = number of samplesn = sample sizecommonly: z = 3

     

    25

    Slide26

    X-bar Chart

    Mean = 5.5.STD = 0.4 ft 99.74% within ± 3 STD(random) 9 students {6.5, 6.4, 6.6, 6.3, 6.7, 6.5, 6.6, 6.4, 6.5} each within “normal”  average = 6.5 ftSample control limits  tighter than populationUCL= = =5.9 ft.GROUP above “normal” (outside control limits)

     

    MIS 373: Basic Operations Management

    5.5

    6.7

    4.3

    5.1

    5.9

    5.5

    6.5

    26

    Slide27

    R-Chart: Control Limits

    Range charts or R-charts are used to monitor process dispersion

    MIS 373: Basic Operations Management

    27

    Slide28

    Mean and range charts

    MIS 373: Basic Operations Management

    (a)

    These

    sampling distributions result in the charts below

    (Sampling mean is shifting upward but range is consistent)

    R-chart

    (

    R

    -chart does not detect change in mean)

    UCL

    LCL

    x

    -chart

    (

    x

    -chart detects shift in central tendency)

    UCL

    LCL

    28

    Slide29

    Mean and range charts

    MIS 373: Basic Operations Management

    R

    -chart

    (

    R

    -chart detects increase in dispersion)

    UCL

    LCL

    (b)

    These sampling distributions result in the charts below

    (Sampling mean is constant but dispersion is increasing)

    x

    -chart

    (

    x

    -chart does not detect the increase in dispersion)

    UCL

    LCL

    29

    Slide30

    Run Tests

    Even if a process appears to be in control, the data may still not reflect a random processAnalysts often supplement control charts with a run testRun testA test for patterns in a sequenceRunSequence of observations with a certain characteristic

    MIS 373: Basic Operations Management

    30

    Slide31

    Run Tests

    MIS 373: Basic Operations Management

    31

    A: Above

    B: Below

    U: Upward

    D: Downward

    Slide32

    Patterns in Control Charts

    MIS 373: Basic Operations Management

    UCL

    Target

    LCL

    Erratic behavior.

    UCL

    Target

    LCL

    Run of 5 above (or below) central line.

    UCL

    Target

    LCL

    Two plots very near lower (or upper) control

    .

    Normal behavior. Process is “in control.”

    UCL

    Target

    LCL

    UCL

    Target

    LCL

    One plot out above (or below).

    Process

    is “out of control.”

    UCL

    Target

    LCL

    Trends in either direction, 5 plots.

    Progressive

    change.

    32

    Slide33

    Demo

    ASQ Control chart template

    http://

    asq.org/learn-about-quality/data-collection-analysis-tools/overview/asq-control-chart.xls

    Slide34

    Key Points

    All processes exhibit random variation. Quality control's purpose is to identify a process that also exhibits nonrandom (correctable) variation on the basis of sample statistics (e.g., sample means) obtained from the process.Control charts and run tests can be used to detect nonrandom variation in sample statistics. It is also advisable to plot the data to visually check for patterns.

    MIS 373: Basic Operations Management

    34

Report this Document.

  • Creating Content

    Creating Content

    725-views
  • Clipper: A Low Latency Online Prediction Serving System

    Clipper: A Low Latency Online Prediction Serving System

    695-views
  • Claims, Evidence, and Warrants

    Claims, Evidence, and Warrants

    605-views
  • You Can Choose Engineered Timber Flooring In Melbourne

    You Can Choose Engineered Timber Flooring In Melbourne

    781-views
  • Gaucho Round-Up

    Gaucho Round-Up

    735-views
  • SCADA in electrical power delivery

    SCADA in electrical power delivery

    754-views
  • A Century of Turmoil

    A Century of Turmoil

    724-views
  • Theories of evolution

    Theories of evolution

    786-views
  • Drones Collecting Cell Phone Data in

    Drones Collecting Cell Phone Data in

    777-views
  • Fossil Collecting:

    Fossil Collecting:

    745-views