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Section VIII. How Do You Show That You Made a Difference?. Did your project reduce variation or shift the mean? How do you demonstrate improvements statistically?. VIII-47. Hypothesis Testing.
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How Do You Show That You Made a Difference? • Did your project reduce variation or shift the mean? • How do you demonstrate improvements statistically? VIII-47
Hypothesis Testing 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). VIII-47
Hypothesis • 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. VIII-47
Hypothesis Basics • 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 VIII-47
Hypothesis Test Process Flow VIII-47
One-way ANOVA example • 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 VIII-83
Two-way ANOVA example • 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 VIII-87