Symbol | Description |
---|---|
A 2 | Multiplier of for calculating -chart control limits |
2 | Multiplier of for calculating -chart control limits |
A 3 | Multiplier of for calculating X -chart control limits |
B 3 | Multiplier of to determine s -chart LCL |
B 4 | Multiplier of to determine s -chart UCL |
C | Number of nonconformities or defects in a specified inspection unit (sample size ) |
C 4 | Factor for estimating ƒ x from |
ƒ 2 | Factor for estimating ƒ x from |
| Factor for estimating ƒ x from |
D | Weighted number of defects (demerits) |
D 3 | Multiplier of R to determine R -chart LCL |
| Multiplier of to determine R -chart LCL |
D 4 | Multiplier of to determine R -chart UCL |
E 2 | Multiplier of m for calculating X -chart control limits |
k | Number of subgroups or samples |
LCL | Lower control limit |
LSL | Lower specification limit |
¼ | True population average "mu" |
n | Sample size: number of items in sample |
np | Number of nonconforming items or defectives in a sample size of n |
p | Proportion or fraction of nonconforming items "fraction defective" |
R | Range: X highest - X lowest |
| Average of sample ranges |
| Median of sample ranges |
Rm | Moving range |
m | Average of the moving range |
S | Sample standard deviation |
| Average of sample standard deviations |
ƒ x | Standard deviation of a frequency distribution of individual measurements [ X' s] |
| Standard deviation of a frequency distribution of sample averages [ 's] |
ƒ ' | True population standard deviation "sigma prime" |
X | A random variable: an individual measurement |
X i | The i th random variable or individual measurement |
| Sample averages: X 1 + X 2 + ... X n / n |
| The i th sample average |
| Average of the averages: "grand averages" |
| True population average: "X-bar prime" = ¼ |
| Sample median |
| Median of the sample medians: "grand median" |
u | Nonconformities or defects per production unit |
U | Weighted number of defects per production unit |
UCL | Upper control limit |
USL | Upper specification limit |
Z | Standardized normal variable = X - ¼ / ƒ x |