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 defective. What would you do?

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