
Quality in Production—Process Control I 227
If an R value is outside its limits and its causes are eliminated, should
the corresponding X value also be eliminated from the data along with the
R value? The answer is yes; it makes sense to eliminate the entire sample
from the data because it came from the process when it was not in-con-
trol� However, it is not always necessary to remove an X value (or R value)
from its chart when removing the corresponding value from the other chart�
Otherwise, when calculations are done with paper and pencil, excessive
arithmetic work may result, and we may nd ourselves going bac