SCO 3001 Midterm 2 – A+ Graded | Real Exam
Questions from University lec
Type I error: - ✔✔concluding a process is "not in control" when it actually is ( risk, producer's risk)
o ~95.4% of sample means within 2
~(100 - 95.4) = 4.6% possibility of being in "tails"
o ~99.7% of sample means within 3
~(100 - 99.7) = 0.3% possibility of being in "tails"
Reduces chance of Type 1 error
Increases chance of Type 2
Type 2 error... - ✔✔Type II error: concluding a process is "in control"
when it actually is not (consumer's risk)
o ~95.4% of sample means within 2
more likely to detect shift of process mean due to nonrandom variability
o ~99.7% of sample means within 3
less likely to detect shift of process mean due to nonrandom variability
• Do I use 2 or 3!?!
Variables: - ✔✔data are measured, usually on a continuous scale.
o Examples: length, width or weight of a part, amount of time needed to complete a task
Attribute: - ✔✔data are counted.
o Examples: the number of defective parts in a sample, the number of calls per day
Statistical Tools - ✔✔• Control charts for variables
o Mean charts (x-bar charts)
o Range charts (R charts)
• Control charts for attributes
,o p-chart
Mean Control Charts - Using Range - ✔✔• Based on the range of sample data R
o Upper control limits:
o Lower control limits:
• where
o Average of sample ranges (R =Xmax-Xmin)
o A2 can be found in table 9.1
• Note: this approach assumes that the range is in control
Range Control Chart (R-Chart) - ✔✔• Control chart used to monitor process dispersion
• where D3 and D4 are obtained from Table 9.1.
Using Mean and Range Charts - ✔✔• Mean charts are sensitive to shifts in the process mean, whereas
range charts are sensitive to changes in process dispersion
• Both charts might be used to monitor the same process
Control Chart for Attributes - ✔✔• Used when the process characteristic is counted rather than
measured
• P chart
Use of p-Charts, p-Charts - ✔✔• When observations can be placed into two categories.
o Good or bad
o Pass or fail
o Operate or don't operate
o Examples: In banking industry, number of non-endorsed deposits or the number of incorrect financial
statements sent to customers, number of bad lightbulbs, number of letters or data entry records typed
with errors.
• When the data consists of multiple samples of several observations each
o e.g., 15 samples of n = 20
, Use of Control Charts - ✔✔• At what point in the process to use control charts
o Have a tendency to go out of control
o Critical to the successful operation of the product/services
• What size samples to take
o Cost and time are functions of sample size
o Smaller samples are more likely to reveal a change in the process
• What type of control chart to use: Variables vs. Attributes
o Measuring is more costly and time-consuming per unit
o Measuring provides more information
o Variable control chart needs a smaller sample size
Total Quality Management - ✔✔• A philosophy that involves everyone in an organization in a continual
effort to improve quality and achieve customer satisfaction.
Three Key Philosophies - ✔✔• Continuous improvement: Never-ending push to improve.
• Involvement of everyone in the organization.
• Customer satisfaction: Meeting or exceeding customer expectations.
• Continuous improvement: - ✔✔Never-ending push to improve.
The TQM Approach - ✔✔• 1) Find out what the customer wants
• 2) Design a product or service that meets or exceeds customer wants
• 3) Design processes that facilitates doing the job right the first time
• 4) Keep track of results
• 5) Extend these concepts to suppliers and to distributers
Six Sigma - ✔✔• Statistically
o Having no more than 3.4 defects per million
Questions from University lec
Type I error: - ✔✔concluding a process is "not in control" when it actually is ( risk, producer's risk)
o ~95.4% of sample means within 2
~(100 - 95.4) = 4.6% possibility of being in "tails"
o ~99.7% of sample means within 3
~(100 - 99.7) = 0.3% possibility of being in "tails"
Reduces chance of Type 1 error
Increases chance of Type 2
Type 2 error... - ✔✔Type II error: concluding a process is "in control"
when it actually is not (consumer's risk)
o ~95.4% of sample means within 2
more likely to detect shift of process mean due to nonrandom variability
o ~99.7% of sample means within 3
less likely to detect shift of process mean due to nonrandom variability
• Do I use 2 or 3!?!
Variables: - ✔✔data are measured, usually on a continuous scale.
o Examples: length, width or weight of a part, amount of time needed to complete a task
Attribute: - ✔✔data are counted.
o Examples: the number of defective parts in a sample, the number of calls per day
Statistical Tools - ✔✔• Control charts for variables
o Mean charts (x-bar charts)
o Range charts (R charts)
• Control charts for attributes
,o p-chart
Mean Control Charts - Using Range - ✔✔• Based on the range of sample data R
o Upper control limits:
o Lower control limits:
• where
o Average of sample ranges (R =Xmax-Xmin)
o A2 can be found in table 9.1
• Note: this approach assumes that the range is in control
Range Control Chart (R-Chart) - ✔✔• Control chart used to monitor process dispersion
• where D3 and D4 are obtained from Table 9.1.
Using Mean and Range Charts - ✔✔• Mean charts are sensitive to shifts in the process mean, whereas
range charts are sensitive to changes in process dispersion
• Both charts might be used to monitor the same process
Control Chart for Attributes - ✔✔• Used when the process characteristic is counted rather than
measured
• P chart
Use of p-Charts, p-Charts - ✔✔• When observations can be placed into two categories.
o Good or bad
o Pass or fail
o Operate or don't operate
o Examples: In banking industry, number of non-endorsed deposits or the number of incorrect financial
statements sent to customers, number of bad lightbulbs, number of letters or data entry records typed
with errors.
• When the data consists of multiple samples of several observations each
o e.g., 15 samples of n = 20
, Use of Control Charts - ✔✔• At what point in the process to use control charts
o Have a tendency to go out of control
o Critical to the successful operation of the product/services
• What size samples to take
o Cost and time are functions of sample size
o Smaller samples are more likely to reveal a change in the process
• What type of control chart to use: Variables vs. Attributes
o Measuring is more costly and time-consuming per unit
o Measuring provides more information
o Variable control chart needs a smaller sample size
Total Quality Management - ✔✔• A philosophy that involves everyone in an organization in a continual
effort to improve quality and achieve customer satisfaction.
Three Key Philosophies - ✔✔• Continuous improvement: Never-ending push to improve.
• Involvement of everyone in the organization.
• Customer satisfaction: Meeting or exceeding customer expectations.
• Continuous improvement: - ✔✔Never-ending push to improve.
The TQM Approach - ✔✔• 1) Find out what the customer wants
• 2) Design a product or service that meets or exceeds customer wants
• 3) Design processes that facilitates doing the job right the first time
• 4) Keep track of results
• 5) Extend these concepts to suppliers and to distributers
Six Sigma - ✔✔• Statistically
o Having no more than 3.4 defects per million
