An operator wants to determine the standard deviation for a machine she operates. To do this, she wants to create a p-chart. Over a month's time, she collects 30 samples of 75 observations each and records the number of errors. The average proportion defective is found to be 0.024. Which of the following is the standard deviation ( ) of the machine?
A) Less than or equal to 0.1
B) More than 0.1 but less than or equal to 0.5
C) More than 0.5 but less than or equal to 1.0
D) More than 1.0

Question

Quizplus · Accepted Answer

The standard deviation (σ) for a p-chart is calculated using the formula σ = sqrt[p(1-p)/n], where p is the average proportion defective, and n is the number of observations per sample. Substituting the given values, σ = sqrt[0.024(1-0.024)/75], which results in a value less than 0.1.

An Operator Wants to Determine the Standard Deviation for a Machine