Quality Advisor
A free online reference for statistical process control, process capability analysis, measurement systems analysis,
control chart interpretation, and other quality metrics.
SPC DEMO
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Data Collection Tools
A resource for data collection tools, including how to collect data, how much to collect, and how frequently to collect it.
Formulas and Tables
SPC DEMO
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Process performance indices
Process performance indices use sigma of the individuals.
Pp
Pp for one-sided specifications
If you are using one sided specifications, use the following formulas to determine the Cp:
Upper specification
Lower specification
Ppk
Pr
Formulas and Tables
SPC DEMO
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Capability indices
Capability indices use estimated sigma.
Cp
Cp for one-sided specifications
If you are using one sided specifications, use the following formulas to determine the Cp:
Upper specification
Lower specification
Cr
Cpk
Cpm
| Where: |  |
T = specification target (nominal)
Xi = a given individual reading of ” i ”
n = total number of individual readings
= symbol for summation
Formulas and Tables
SPC DEMO
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t-chart formula
The t-chart formula:
Formulas and Tables
SPC DEMO
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g-chart formula
The g-chart formula:
Formulas and Tables
SPC DEMO
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c-chart formulas
The c-chart formula (for number of nonconformities, from subgroups of a constant size):
Formulas and Tables
SPC DEMO
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u-chart formula
The u-chart formula (for number of nonconformities from subgroups that can vary in size):
Formulas and Tables
SPC DEMO
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p-chart formulas
The p formula (for the proportion of nonconforming units from subgroups that can vary in size):
To calculate control limits for the p-chart:
Formulas and Tables
SPC DEMO
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np-chart formulas
The np-chart formula (for number of nonconforming units from subgroups with a constant size):
