# Symbols and Denominations

These are the symbols and denominations used in the software GUI.

Symbols | Description
--- | ---
CL | Center line
Cp | Process capability index
Cpk | Minimum process capability index
k | Number of subgroups
LCL | Lower control limit
LSL | Lower specification limit for the product
n | Subgroup sample size
N | Total number of observations
R | Range of the subgroup observations: difference between the largest and smallest observed value
Ṙ | Arithmetic average of the R values for the subgroups
s | Sample standard deviation within the subgroup
St | Sample (total/overall) standard deviation
σ | Standard deviation for the population from which samples are taken
σ̂ | Estimated standard deviation for the population from which samples are taken
σt | Estimated (total/overall) standard deviation
UCL | Upper control limit
USL | Upper specification limit for the product
X | Measured quality characteristic value, different observed values denoted with X1, X2 .., XN
̅X̅ | Arithmetic average of subgroup sample observations
̿X̿ | Total arithmetic average of the sample observations