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Section VIII

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Did your project reduce variation or shift the mean?

How do you demonstrate improvements statistically?

How Do You Show That You Made a Difference?

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The question one needs to ask during a project is whether the changes made as the result of a Black Belt project have made a difference in the process.

The question is, “Has the project made a difference, and if so, how confident are we that the difference is statistically significant?”

We strive for 95% confidence or better (α=.05).

Hypothesis Testing

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A hypothesis is: ◦ a tentative explanation for an observation

that can be tested by further investigation.◦ taken to be true for the purpose of

investigation; an assumption.

Examples:◦ Average gas mileage differs depending on

type A or B gas.

◦ Probability of death in auto accidents differs depending on seat belt usage.

◦ The type of aspirin determines the amount of pain relief.

◦ A Six Sigma Black Belt project produced significant results with regard to mean and/or standard deviation improvement.

Hypothesis

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We set up 2 hypotheses◦ H0 is called the null hypothesis

what is being tested must contain an = assumed to be true

◦ H1 is called the alternate hypothesis Based on the data we collect, we

must decide in favor of either H0 or H1. Which does the evidence support?◦ You can only reject null, or fail to

reject null

Hypothesis Basics

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Hypothesis Test Process Flow

Define the problem and state objectives

State a “Null Hypothesis” (Ho)

State the “Alternative Hypothesis” (H1)

Establish significance level (a) and determine the critical value

Collect sample data

Calculate test statistic and/or p-value

DECIDE:What does the evidence

suggest?

Reject Ho? or Fail to reject Ho?VIII-47

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Set up the statapult and reduce obvious variation

Pick a factor that you would like to test◦ Ball type◦ Operator◦ Etc

Pick at least 3 different treatments (levels)

Record data with at least 5 data points each population

Analyze

One-way ANOVA example

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Set up the statapult and reduce obvious variation

Pick two factors that you would like to test◦ Ball type◦ Operator◦ Pull back angle◦ Etc.

Pick at least 2 different levels for each factor

Record at least 5 data points each

Analyze

Two-way ANOVA example

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