Control charts are a popular way to statistically monitor a processes' performance. They are used for both variables (i. quantitative measures) and...

Control charts are a popular way to statistically monitor a processes' performance. They are used for both variables (i.e. quantitative measures) and attributes (qualitative measures). The underlying statistical distribution for a p-chart (yes-no attribute) is Binomial. Although, large samples can be approximated by a Normal (bell-shaped) distribution! Why is this true?