I want to Apply Tests for Special Causes in the p-chart, but the sample size for each group is different. So, I don’t have a fixed UCL and LCL, and I will get the following warning with below code: WARNING: Asymmetric control limits encountered for yes_answer1 for at least one subgroup. proc shewhart data=tmp2;
pchart yes_answer1*quarter / subgroupn = total_count1
tests =1 to 8
TESTNMETHOD=STANDARDIZE
table
tablelegend;
run; Note: The SHEWHART procedure provides an option for working with unequal subgroup sample sizes. For example, I can use the LIMITN= option to specify a fixed (nominal) sample size for computing the control limits. Below is the sample size for each group that I have; my question is, how can I choose the number for LIMITN? quarter Subgroup 2021Q3 30 2021Q4 66 2022Q1 54 2022Q2 66 2022Q3 69 2022Q4 74 2023Q1 83 2023Q2 96
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