Question 1

Discuss the three basic quality control practices used in manufacturing.

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Question 2

Describe the steps required to develop and use control charts.

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Question 3

What is the purpose of a process-capability study and what is a process capability index?

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Question 4

An airline found that on average, 0.62% of the luggage they received from passengers at LAX( Los Angeles Airport) is lost or damaged. On a typical day, 1000 pieces of luggage pass through this airport. The upper control limits for a p chart for monitoring the daily fraction nonconforming?

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Question 5

The time to check out guests at a hotel was measured over the course of several weeks. Management believes that the target time for checking out guests should be between 2 and 4 minutes with a target of 3 minutes. The data gathered had a mean time of 2.75 minutes with a standard deviation of 0.4 minutes. Find and interpret C_p, C_pl, C_pu, and C_pk in the context of this situation.

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Question 6

A bottling machine fills soft drink bottles with an average of 12.000 ounces with a standard deviation of 0.002 ounces. Determine the process capability index, C_p, if the design specification for the fill weight of the bottles is 12.000 ounces plus or minus 0.015 ounces.

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Question 7

Over several days, 25 samples of 100 items each were tested for electrical resistance. A total of 60 items failed. Determine $\bar { p }$ and the control limits for a p chart.

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Question 8

Explain the issues associated with selecting the appropriate sample size and sampling frequency for control charts.

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Question 9

Discuss the difference between a continuous metric and a discrete metric, give examples of each, and list the common control charts associated with each.

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Question 10

Find the control limits for a c chart with $\bar { C }$ = 7.

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Question 11

A Procter and Gamble factory process fills boxes with detergent. Construct an appropriate set of control charts to monitor the process. Historical data for fill weight in ounces) of eight samples is presented below. A sample size of six was used.
 $$\begin{array} {  c  c  c  } 
 \text { Sample } & \text { Sample Mean } & \text { Sample Range } \
\hline1 & 15.80 & 0.42 \
 2 & 16.10 & 0.38 \
 3 & 16.02 & 0.08 \
 4 & 15.95 & 0.15 \
 5 & 16.12 & 0.42 \
6 & 16.18 & 0.23 \
 7 & 15.87 & 0.36 \
 8 & 16.20 & 0.40 \

\end{array}$$ 
a.Compute the limits for both an R chart and x-bar chart. Compare the sample results to the limits of the charts.
b.Briefly explain what the quality control charts tell you. What actions, if any, would you take?

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Question 12

A manufacturing company has a production process that has a target percent nonconforming of 4% which was developed based on numerous samples of 200 observations each. They want to develop control charts using 3 standard deviation limits.
a. What is the center line for the p chart?
b. What is the upper control limit for a p chart?
c. What is the lower control limit for a p chart?

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Question 13

In general, discuss how to interpret control charts.

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Question 14

A manufacturer inspected 40 circuit boards and found a total of 640 defects. If the company wants to use SPC to control the manufacturing process by monitoring the number of defects per circuit board, what type of chart should they use and what should the control limits be?

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Question 15

A company is measuring the time it takes to complete an order. Twenty five samples of size 6 resulted in an average time of 80 minutes with an average range of 20 minutes. Find control limits for the appropriate control charts) that would be used to monitor this process.

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Question 16

Flaws are counted on a standard steel plate sheet). Each sheet has the exact same dimensions. Ten sheets are selected at random and the number of flaws per sheet is as follows.
 $$\begin{array} { c c } 
\text { Sheet } & \text { Number af Flaws } \
\hline 1 & 3 \
2 & 1 \
3 & 3 \
4 & 0 \
5 & 2 \
6 & 2 \
7 & 0 \
8 & 1 \
9 & 1 \
10 & 2
\end{array}$$ 
Determine the lower and upper control limits for a c chart..

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Question 17

Fifteen samples of size 5 have been taken from a production process. The sum of the sample averages was found to be 92.54 cm while the sum of the ranges was 115.36. Find the values of the center lines for the x-bar and R charts.

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Question 18

An operator has determined what her percent defectives is for the machine which she operates. Based on several samples of 75 observations, she found p-bar to be 10%. She wants to set up a control chart using 3 standard deviation control limits.
a. What is the upper control limit for a p chart?
b. What is the lower control limit for a p chart?

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Question 19

Define Statistical Process Control (SPC) and differentiate between common cause and (special or assignable) cause variation.

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Question 20

A production process is sampled 24 times with a sample size of 6 yields an overall mean of 25.2 and an average range of 0.8. Determine the control limits for the x-bar and R charts.

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Quiz 16: Quality Control and Spc