The Chi-Squared test is used to check whether there is a significant difference between observed frequencies (discrete data) and expected frequencies for two or more groups (discrete data). For small sample sizes, Fisher’s Exact test is to be used instead. Both test are performed in a similar way. See for yourself.…
Three teams compete in our CHL business simulation. After completing Day One, it looks like the teams show a very different performance. Although the means look very similar, the variation is strikingly different. To test this assumption of different variation among the teams, the Test for Equal Variances is deployed.…
Consider a production process that produced 10,000 widgets in January and experienced a total of 112 rejected widgets after a quality control inspection. A project was deployed to fix this problem. In April, the process produced 8,000 widgets and experienced a total of 63 rejects. Did the process really improve? Read..…
Linear regression is one of the most commonly used hypothesis tests in Lean Six Sigma work. Linear regression offers the statistics for testing whether two or more sets of continuous data correlate with each other, i.e. whether one drives another one. Additionally, it shows the influence of discrete variables, too.…
ANOVA (analysis of variances) is a statistical technique for determining the existence of differences among several population means. The technique requires the analysis of different forms of variances – hence the name. It is testing whether means are different. Read about an application example here.…
In some situations, Six Sigma practitioners find a Y that is discrete and Xs that are continuous. How can a regression equation be developed in these cases? Black Belt training indicated that the correct technique is something called logistic regression or binary regression. But this tool is often not well understood.…
More often than not, Lean Six Sigma practitioners have to find out whether two groups that look quite the same are really the same. If averages of two groups are in question and the data is continuous and normally distributed, the two-sample t-test offers an answer to the question. Read how to run this test in SigmaXL.…
Measurement error is unavoidable. There will always be some measurement variation due to the measurement system itself. Most problematic measurement system issues occour when measuring attribute data by relying on human judgment such as good/bad, pass/fail. Attribute Gage R&R helps to find and reduce these errors.…
Lean Government. Even to the seasoned Lean practitioner, this idea sounds far-fetched. Governments are traditionally seen as the epitome of bureaucracy and red tape, incomprehensible forms and endless queues. But there are workable Lean strategies for governments seeking to reduce waste. Eight are outlined here.…
Rejecting a null hypothesis when it is false is what every good hypothesis test should do. The “power of the test” is the measure of how good a test is.…
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