December 23, 201114 yr I am doing a project on Dmaic in a manufacturing company. They produce 32000 components a month. They dont find mean and standard deviation of that component. I want to determine sample size for that lot. How do I find sample size?
January 4, 201214 yr Hi Sam, More close we are to the population more accurate is our estimate. This means if we take a sample closer to 32000 (population) more close we get to the real data. If you want to use Normal Distribution ideally your sample should be greater than 30. I would suggest you take 2 samples of 300-400 each and determine the SD and mean. You can check how correct or incorrect is the data by using Hypothesis Testing. Remember to use Standard Error of mean (SE) instead of SD as you are dealing with the sample. Regards, Rohit
July 22, 20232 yr You need to provide more information to determine the sample size. E.g. you could define a confidence level and a max. width of the associate confidence interval of the average value. Or you define a confidence level and a max. allowed relative deviation of the standard deviation. There are many options, but you have to decide what suites your needs. A good reference is Hahn & Meeker: "Statistical intervals".
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