Hi everyone,
I want to Apply Tests for Special Causes in 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;
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 I can choose the number for LIMITN.
quarter Subgroup
2021Q3 30
2021Q4 66
2022Q1 54
2022Q2 66
2022Q3 69
2022Q4 74
2023Q1 83
2023Q2 96
Thanks
- Badges
- Science topic
- Similar topics
- Statistics
- Survey