Statistical Sampling

Statistical sampling involves taking a sample number of parts from the whole population and examining them to determine whether they fall within acceptable variances. The formula to calculate the correct sample size is beyond the scope of this book. However, Creative Research Systems has an online calculator and an explanation of statistical sampling that you might find useful. You can find them at http://www.surveysystem.com/sscalc.htm.

Perhaps you determine to statistically sample 25 parts out of a lot or run. The quality plan outlines that the lot will pass if four parts or fewer fall outside the allowable variance.

Statistical sampling might also involve determining the standard deviation for a process, as discussed in the control chart tool and technique. The quality plan determines whether plus or minus two standard deviations—95.44 percent of the population—is adequate or whether plus or minus three standard deviations—99.73 percent—is adequate.

Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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