From the course: Six Sigma: Black Belt
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Sample sizes
- In the measure phase of a Six Sigma project, the project team needs to collect data to measure the baseline performance of Y. Since it's not always possible to measure every item in the population, samples are collected. So you might be wondering, "How do you sample?" And, "How much do you sample?" How to sample is called sampling strategy, which I cover in other Six Sigma courses. How much to sample brings us to the question: what should be the sample size? The sample size determination depends on whether the type of data to be collected is continuous or discrete. If the type of data is continuous, you probably need to sample from the process to estimate the mean, such as the mean processing time of invoices. Here is a sample size to estimate the mean with 95% confidence. Where Z is from the normal distribution, and 1.96 is the Z value for a 95% confidence level. And S is a standard deviation, and D is the precision. So how precise do you want the estimate to be? If you want the…
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