Use this chart to determine the Upper Control Limit(UCL) and Lower Contrl Limit(LCL) for a NP chart.NP chart is used when you have Defects data with a fixed Sample size

Average Defective Proportion(p-bar)

Calculate the average defective portion across all samples

Number of observations

Enter the number of observations in each sample.Since it is fixed sample size,the number of observations will be same in all samples