Hi everyone,
I've created a p-chart to monitor a binary variable on a quarterly basis. But I noticed a p-chart requires at least 20 data points. So, I've shifted to monthly reporting.
with this adjustment I have reduction in the number of obs per subgroup when moving from quarterly to monthly charts.
Could you please see the attached file and advise if the sample sizes per subgroup are adequate for generating a reliable p-chart?
Thank you!