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Slides by

SpirosVelianiti

sCSUS

Deming’s Red Bead Deming’s Red Bead ExperimentExperiment

“…“….. Stupidly simple….. .. Stupidly simple….. The messages learned The messages learned

are not”are not”

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Summary SlideSummary Slide

Red Bead Experiment ExerciseRed Bead Experiment Exercise Use of STATGRAPHICS to analyze the resultsUse of STATGRAPHICS to analyze the results VariationVariation Common vs. Specific (Assignable) Causes Common vs. Specific (Assignable) Causes Stable and Unstable Processes Stable and Unstable Processes Lessons Learned from the Red Bead ExperimentLessons Learned from the Red Bead Experiment

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Red Bead Experiment Exercise (step 1)Red Bead Experiment Exercise (step 1)

BackgroundBackground

1.1. I need 4 students to represent I need 4 students to represent factory workersfactory workers

• One is “middle management”One is “middle management”

• Three are newly hired Three are newly hired “Factory Workers”“Factory Workers”

• Teacher is the CEOTeacher is the CEO

2.2. Factory workers will be Factory workers will be employed for 10 days on employed for 10 days on probationprobation

3.3. In order for the factory to be In order for the factory to be cost effective, workers must cost effective, workers must produce no more than 8 produce no more than 8 defective (red bead) items out defective (red bead) items out of 50 items produced per day of 50 items produced per day

Here is our work dayHere is our work day Factory Workers – Produce Factory Workers – Produce

daily productsdaily products Middle management – Middle management –

Records daily production Records daily production defects (red beads)defects (red beads)

After the 10 day productionAfter the 10 day production Top management, middle Top management, middle

management, and consultants management, and consultants (class) will construct a time (class) will construct a time series plot of the number of series plot of the number of defects (red beads).defects (red beads).

We will look for trendsWe will look for trends

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Red Bead Experiment Exercise (step 2)Red Bead Experiment Exercise (step 2)

Management DecisionsManagement Decisions

1.1. We will allow our factory We will allow our factory workers to work for one more workers to work for one more week (5 days of production)week (5 days of production)

2.2. Necessary management Necessary management decisions are made (class decisions are made (class does not know what we does not know what we decided)decided)

Here is our work day for week 3Here is our work day for week 3 Factory Workers – Produce daily Factory Workers – Produce daily

productsproducts Middle management – Records Middle management – Records

daily production defects (red daily production defects (red beads)beads)

After another 5 day productionAfter another 5 day production Extend the time series plot of Extend the time series plot of

the number of defects (red the number of defects (red beads) to include the last 5 beads) to include the last 5 production defectsproduction defects

We will look for trendsWe will look for trends We will examine the time series We will examine the time series

plotplot

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Red Bead Experiment Exercise (step 3)Red Bead Experiment Exercise (step 3)

Statistical analysis we will Statistical analysis we will perform (identification perform (identification

tools)tools) StationaryStationary

Constant MeanConstant Mean

Constant VarianceConstant Variance

Time Series PlotTime Series Plot Independence (Random)Independence (Random)

Runs Up and Down Runs Up and Down TestTest

NormalityNormality

Shapiro-Wilks TestShapiro-Wilks Test

In STATGRAPHICS we wilIn STATGRAPHICS we wil Test stationary:Test stationary:

DTD: Describe -> Time-Series DTD: Describe -> Time-Series -> Descriptive Methods-> Descriptive Methods

Test Independence:Test Independence: Runs Up and Down TestRuns Up and Down Test Tables Options (3 T’s): select Tables Options (3 T’s): select “ “Tests for Randomness”Tests for Randomness” Test Normality:Test Normality: DDF: Describe -> Distribution DDF: Describe -> Distribution

Fitting -> Fitting Uncensored Fitting -> Fitting Uncensored DataData

Tables Options: select “Tests Tables Options: select “Tests for Normality”for Normality”

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Lessons LearnedLessons Learned(slides that follow(slides that follow

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VARIATIONVARIATION

COMMONCOMMON

Numerous small Numerous small causes of causes of variability that variability that are inherent to are inherent to any system, any system, operate operate randomly or by randomly or by chancechance

SPECIFICSPECIFIC

Assignable, have Assignable, have relatively large relatively large effects on effects on process, occur process, occur occasionally or occasionally or sporadicsporadic

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Common vs. Specific (Assignable) Common vs. Specific (Assignable) CausesCauses

The variation in the quality of the production The variation in the quality of the production output is due to either common causes or specific output is due to either common causes or specific (assignable) causes.(assignable) causes.

Common causes: normal or natural variations in Common causes: normal or natural variations in process outputs that are due purely to chance. No process outputs that are due purely to chance. No corrective action is necessary when output corrective action is necessary when output variations are due to common causes.variations are due to common causes.

Specific (Assignable) causes: Variation in process Specific (Assignable) causes: Variation in process outputs that are due to special circumstances or outputs that are due to special circumstances or factors (machine tools wearing out, incorrect factors (machine tools wearing out, incorrect machine settings, poor-quality raw materials, machine settings, poor-quality raw materials, operator error, etc.)operator error, etc.)

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Stable and Unstable ProcessesStable and Unstable Processes

A process is A process is StableStable when when variationvariation made made up of only common causesup of only common causes

In an In an UnstableUnstable process (process is not in process (process is not in statistical control), variation is made up statistical control), variation is made up of both common causes and specific of both common causes and specific causes causes

Identification Tools are used to find if Identification Tools are used to find if specific causes of variation exist within specific causes of variation exist within a processa process

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Lessons Learned from the Red Bead Lessons Learned from the Red Bead ExperimentExperiment

Variation is an inherent part of any processVariation is an inherent part of any process Only management can change the processOnly management can change the process Identification tools (time series plots, non Identification tools (time series plots, non

parametric runs up and down test, and the parametric runs up and down test, and the Shapiro-Wilk test) can help us identify specific Shapiro-Wilk test) can help us identify specific variationvariation

Workers work within a system over which they Workers work within a system over which they have little control. The system determines their have little control. The system determines their performance.performance.

The work standard set by management may The work standard set by management may have no relationship to the capability of the have no relationship to the capability of the system.system.

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Summary SlideSummary Slide

Red Bead Experiment ExerciseRed Bead Experiment Exercise Use of STATGRAPHICS to analyze the resultsUse of STATGRAPHICS to analyze the results VariationVariation Common vs. Specific (Assignable) Causes Common vs. Specific (Assignable) Causes Stable and Unstable Processes Stable and Unstable Processes Lessons Learned from the Red Bead ExperimentLessons Learned from the Red Bead Experiment