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.

Question

Quizplus · Accepted Answer

The sample proportion of defective bars (0.07) is significantly higher than the historical average (0.015). With z = 3, this indicates the sample is outside the control limits, suggesting an assignable cause rather than random variation.

Historically, the Average Proportion of Defective Bars Has Been 0