Exam 26: Statistical Process Control

In the table below are selected values for the OC curve associated with the acceptance sampling plan n = 50, c = 1. (Watch out-the points are not evenly spaced.) Assume that upon failed inspection, defective items are replaced. Calculate the AOQ for each data point. (You may assume that the population is much larger than the sample.) Plot the AOQ curve. At approximately what population defective rate is the AOQ at its worst? Explain how this happens. How well does this plan meet the specifications of AQL = 0.0050, α = 0.05; LTPD = 0.05, β = 0.10? Discuss. Population percent defective Probability of acceptance 0.005 0.97387 0.01 0.91056 0.02 0.73577 0.03 0.55528 0.04 0.40048 0.05 0.27943 0.06 0.19000 0.08 0.08271

Acceptance sampling

The Central Limit Theorem

The c-chart signals whether there has been a

The normal application of a p-chart is in

An x-bar control chart was examined and no data points fell outside of the limits. Can this process be considered in control?

Acceptance sampling accepts or rejects an entire lot based on the information contained in the sample.

What is acceptance sampling?

A woodworker is concerned about the quality of the finished appearance of her work. In sampling units of a split-willow hand-woven basket, she has found the following number of finish defects in ten units sampled: 4, 0, 3, 1, 2, 0, 1, 2, 0, 2. a. Calculate the average number of defects per basket b. If 3-sigma control limits are used, calculate the lower control limit, centerline, and upper control limit.

A retail store manager is trying to improve and control the rate at which cashiers sign customers up for store credit cards. After posting a p-chart of the store's credit card sign-ups the manager takes new samples of size 50 three weeks later. He finds that each sample of 50 contained 5 credit card signups on average. Find p-bar and 99.73% control limits.

At your first job out of college you have been assigned to the production of bottled 20 oz. soda. The process has upper and lower limits of 20.5 and 19.5 oz, respectively, with a mean of 19.8 oz And standard deviation of .3 oz. Your manager has requested the process produce no more than 3.4 Defects per 1 million bottles produced. Calculate C_pk and then determine if the process is capable Or if you should be looking for assignable variation.

Briefly explain what the Central Limit Theorem has to do with control charts.

To measure the voltage of batteries, one would sample by attributes.

In acceptance sampling, a manager can reach the wrong conclusion if the sample is not representative of the population it was drawn from.

The steeper an Operating Characteristics curve, the better it discriminates between good and bad lots.

Which of the following is true regarding the average outgoing quality level?

What is the purpose of the Operating Characteristics curve?

Pierre's Motorized Pirogues and Mudboats is setting up an acceptance sampling plan for the special air cleaners he manufactures for his boats. His specifications, and the resulting plan, are shown on the POM for Windows output below. Pierre is a bit confused. He mistakenly thinks that acceptance sampling will reject all bad lots and accept all good lots. Explain why this will not happen.

Statistical process control charts

In most acceptance sampling plans, when a lot is rejected, the entire lot is inspected and all defective items are replaced. When using this technique the AOQ