Is the constraint for not using variable subgroup sizes in Xbar-R chart only the sigma estimator?.Is it possible to have the Xbar-R chart even with varying subgroup size? Since I am measuring all the products that pass through my process, I have varying sub group size. If it is a sample, then is my only option I-MR charts? sampling a sample doesn't make a lot of sense to me.Īfter discussion with whuber, I have decided to rephrase my question. Can I use in someway, all the observation in an Xbar R Chart? without sampling (cause if I choose a rational subgroup as a day, the subgroup sizes are variable and that won't fit in to the standard calculationsĤ. But is that designed keeping in mind the computational and operational complexities of measuring each and every product and calculating? or is there a more statistical reason behind it?ģ. If it is a population, then the question is should I sample or not? I know X bar and R charts are based on sampling. So, now since I'm measuring all the products that pass through the process, am I looking at the population or the sample?Ģ. I have a process for which a lot of variables are measured, and every product that goes through the process is measured for these variables (since it is an automated testing).ġ. Now that I have set the background, I'll come to the question:
#XBAR R CHART EXAMPLE HOW TO#
I am aware of how to apply the control limits, but not really sure about the statistical background behind it.
I am using control limits to check if a process is going out of control or not and detect the mean shifts over time.
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