Historically,the Average Proportion of Defective Bars Has Been 0

Multiple Choice

Historically,the average proportion of defective bars has been 0.015.Samples will be of 100 bars each.Construct a p-chart using z = 3.Suppose a sample had 0.07 defectives.What would you do?

A) Nothing;it is just random variation.
B) Look for assignable causes.
C) Change z to 2 and take another sample.
D) Change z to 4 and continue sampling.