Question 1

The Central Limit Theorem states that when the sample size increases,the distribution of the sample means will approach the normal distribution.

Accepted Answer

A) True 
 B)False

Question 2

Plots of sample ranges indicate that the most recent value is below the lower control limit.What course of action would you recommend?

Accepted Answer

A) Since there is no obvious pattern in the measurements,variability is in control. 
B) One value outside the control limits is insufficient to warrant any action. 
C) Lower than expected dispersion is a desirable condition; there is no reason to investigate. 
D) The process is out of control; reject the last units produced. 
E) Variation is not in control; investigate what created this condition. 
A) Since there is no obvious pattern in the measurements,variability is in control. 
B) One value outside the control limits is insufficient to warrant any action. 
C) Lower than expected dispersion is a desirable condition; there is no reason to investigate. 
D) The process is out of control; reject the last units produced. 
E) Variation is not in control; investigate what created this condition.

Question 3

What is the basic objective of a process control system?

Accepted Answer

It is to provide a s

Question 4

The purpose of process control is to detect when natural causes of variation are present.

Accepted Answer

A) True 
 B)False

Question 5

The purpose of an x-bar chart is to determine whether there has been a:

Accepted Answer

A) change in the dispersion of the process output. 
B) change in the percent defective in a sample. 
C) change in the central tendency of the process output. 
D) change in the number of defects in a sample. 
E) change in the AOQ. 
A) change in the dispersion of the process output. 
B) change in the percent defective in a sample. 
C) change in the central tendency of the process output. 
D) change in the number of defects in a sample. 
E) change in the AOQ.

Question 6

The ________ is the lowest level of quality that we are willing to accept.

Accepted Answer

AQL or acc

Question 7

A hospital-billing auditor has been inspecting patient bills.While almost all bills contain some errors,the auditor is looking now for large errors (errors in excess of $250).Each day last week,the auditor examined 100 bills and found an average defect rate of 16%.Calculate the upper and lower limits for the billing process for 99.73% confidence.

Accepted Answer

0.16 plus or minus (

Question 8

A consultant has been brought in to a manufacturing plant to help apply Six Sigma principles.Her first task is to work on the production of rubber balls.The upper and lower spec limits are 21 and 19 cm,respectively.The consultant takes ten samples of size five and computes the sample standard deviation to be .7 cm and the sample mean to be 19.89 cm.Compute Cp and Cpk for the process.Give the consultant advice on what to do with the process based on your findings.

Accepted Answer

Cp = (21 - 19)/(6*.7)= .476 Cp

Question 9

What is the AOQ of an acceptance sampling plan?

Accepted Answer

The AOQ is the average outgoin

Question 10

The Central Limit Theorem:

Accepted Answer

A) is the theoretical foundation of the c-chart. 
B) states that the average of assignable variations is zero. 
C) allows managers to use the normal distribution as the basis for building some control charts. 
D) states that the average range can be used as a proxy for the standard deviation. 
E) controls the steepness of an operating characteristic curve. 
A) is the theoretical foundation of the c-chart. 
B) states that the average of assignable variations is zero. 
C) allows managers to use the normal distribution as the basis for building some control charts. 
D) states that the average range can be used as a proxy for the standard deviation. 
E) controls the steepness of an operating characteristic curve.

Question 11

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

Accepted Answer

It provides the theoretical foundation f

Question 12

A small,independent amusement park collects data on the number of cars with out-of-state license plates.The sample size is fixed at n=25 each day.Data from the previous 10 days indicate the following number of out-of-state license plates:
   (a)Calculate the overall proportion of "tourists" (cars with out-of-state plates)and the standard deviation of proportions.
(b)Using ±3σ limits,calculate the LCL and UCL for these data.
(c)Is the process under control? Explain.

Accepted Answer

(a)p-bar is 56/250 = 0.224; the standard

Question 13

A nationwide parcel delivery service keeps track of the number of late deliveries (more than 30 minutes past the time promised to clients)per day.They plan on using a control chart to plot their results.Which type of control chart(s)would you recommend?

Accepted Answer

A) both x-bar chart and R-chart 
B) p-chart 
C) c-chart 
D) x-bar chart 
E) both p-chart and c-chart 
A) both x-bar chart and R-chart 
B) p-chart 
C) c-chart 
D) x-bar chart 
E) both p-chart and c-chart

Question 14

A manager wants to build 3-sigma x-bar control limits for a process.The target value for the mean of the process is 10 units,and the standard deviation of the process is 6.If samples of size 9 are to be taken,what will be the upper and lower control limits,respectively?

Accepted Answer

A) -8 and 28 
B) 16 and 4 
C) 12 and 8 
D) 4 and 16 
E) 8 and 12 
A) -8 and 28 
B) 16 and 4 
C) 12 and 8 
D) 4 and 16 
E) 8 and 12

Question 15

The mean and standard deviations for a process are μ = 90 and σ = 9,respectively.For the variable control chart,a sample size of 16 will be used.Calculate the standard deviation of the sample means.

Accepted Answer

Sigma x-ba

Question 16

The number of late insurance claim payouts per 100 should be measured with what type of control chart?

Accepted Answer

A) x-bar chart 
B) R-chart 
C) p-chart 
D) c-chart 
E) either p-chart or c-chart 
A) x-bar chart 
B) R-chart 
C) p-chart 
D) c-chart 
E) either p-chart or c-chart

Question 17

A(n)________ is a graph that describes how well an acceptance plan discriminates between good and bad lots.

Accepted Answer

OC or oper

Question 18

A quality analyst wants to construct a sample mean chart for controlling a packaging process.He knows from past experience that the process standard deviation is two ounces.Each day last week,he randomly selected four packages and weighed each.The data from that activity appear below.
   (a)Calculate all sample means and the mean of all sample means.
(b)Calculate upper and lower 2-sigma x-bar chart control limits that allow for natural variations.
(c)Based on the x-bar chart,is this process in control?

Accepted Answer

(a)The five sample means are 23,21,20,19

Question 19

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:

Accepted Answer

A) worsens (AOQ becomes a larger fraction). 
B) improves (AOQ becomes a smaller fraction). 
C) is not affected,but the AQL is improved. 
D) is not affected. 
E) falls to zero. 
A) worsens (AOQ becomes a larger fraction). 
B) improves (AOQ becomes a smaller fraction). 
C) is not affected,but the AQL is improved. 
D) is not affected. 
E) falls to zero.

Question 20

Some degree of variability is present in almost all processes.

Accepted Answer

A) True 
 B)False

Exam 20: Statistical Process Control

The Central Limit Theorem states that when the sample size increases,the distribution of the sample means will approach the normal distribution.

Plots of sample ranges indicate that the most recent value is below the lower control limit.What course of action would you recommend?

What is the basic objective of a process control system?

The purpose of process control is to detect when natural causes of variation are present.

The purpose of an x-bar chart is to determine whether there has been a:

The ________ is the lowest level of quality that we are willing to accept.

What is the AOQ of an acceptance sampling plan?

The Central Limit Theorem:

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

A nationwide parcel delivery service keeps track of the number of late deliveries (more than 30 minutes past the time promised to clients)per day.They plan on using a control chart to plot their results.Which type of control chart(s)would you recommend?

A manager wants to build 3-sigma x-bar control limits for a process.The target value for the mean of the process is 10 units,and the standard deviation of the process is 6.If samples of size 9 are to be taken,what will be the upper and lower control limits,respectively?

The mean and standard deviations for a process are μ = 90 and σ = 9,respectively.For the variable control chart,a sample size of 16 will be used.Calculate the standard deviation of the sample means.

The number of late insurance claim payouts per 100 should be measured with what type of control chart?

A(n)________ is a graph that describes how well an acceptance plan discriminates between good and bad lots.

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:

Some degree of variability is present in almost all processes.

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