Control Charts
Two main categories of control charts (classified by type of data)
What are Variable and Attribute
The ratio of specification to six standard deviations (short term)
What is Cp or Process Capability
A graph used to study how a process changes over time
What is control chart
x-bar=10
sigma = 0.25
A visual snapshot that graphs the frequency of occurrence
What is a Histogram
A variable control chart with a small sample size (<5)
What is X-bar Chart
Parameters that when equal, indicate that the process is centered
What are Cp and Cpk
Usual/natural historical and quantifiable variation within a system
What is Common Cause Variation
x-bar = 18.6
sigma = 0.68
A chart that displays the number of nonconformances by frequency and with a cumulative percentage curve
What is a Pareto Chart
A variable control chart used for slow production rate processes
What is I or X Chart
The Cp value that indicates that the tolerance limits are equal to the specification limits
What is 1
Qualitative data based on discrete counts
What is Attribute Data
x-bar = 15.2
sigma = 0.218
Cpk = -0.3058
The Cp threshold that indicates that the tolerance limits are greater than the specification limits
What is < 1
Attribute control chart with pass/fail data and a constant sample size
What is np chart
The Cpk value that indicates that the process mean is equal to one of the specification limits
Limits that define the area 3 standard deviations above and below the center-line/average
What are Control Limits
You count the number of voids on each composite part. The spec calls for no more than 20 voids per part and c-bar = 9. What is your UCL of your process?
Attribute control chart with pass/fail data and a variable sample size
What is p Chart
Two variables that are used to determine the control limits for all control charts
The acceptable value of Cp and Cpk
What is ≥ 1.33
A principle that states that 80% of defects or problems usually arise from about 20% of the causes
What is The Pareto Principle
Every 100 parts you record how many passed. What is the UCL of your process if np-bar = 10?
If the specifications are 12.2 ± 0.2 inches, what is the process capability index?
x-bar = 12.0
sigma = 0.1
Cpk = 0