# Control limits for varying subgroup sizes

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#### Hybrid02

I'm trying to create a control chart. I have 4 sample groups with different numbers of parts in each group. When trying to construct a control chart and picking the right constant I need "n" the problem is, is that n is different for each sub group. Can I not construct the control chart using this forumula if each subgroup has a different number of parts?

DaRe DaVil

#### Steve Prevette

##### Deming Disciple
Staff member
Super Moderator
Re: Reliability of a System - Estimation of R(t) having constant failure rate "Lambda

What are you trying to accomplish? Is this a test of the difference between the four groups (better done by test of hypothesis / ANOVA) or do you have a time sequence going on and you want to analyze the time trend in failures (SPC)?

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