Analytical Variation Flashcards
chance / unpredicatable cause
does not recur
random error
one-time error
random error
affects precision;
violation of 1^2s, 1^3s, R^4s
random error
recurring error
systematic error
affects all results
systematic error
affects accuracy; indicated by shift, trend or 2^2s, 4^1s, 8^1s, 10x̄
systematic error
abrupt change
accumulate on one side
6 consecutive days
shift
gradual change
increase or decrease for 6 consecutive days
passing through mean
trend
highly deviating control values caused by random or systematic errors
outliers
mean; y axis
run number; x axis
CUSUM chart
interlab comparison of monthly means
Tonks-Youden plot
most commonly used QC chart
Levy-Jennings chart
1 ctrl value exceeds ±2SDs
warning rule
initiates testing of other rule
1-2s
1-2s
error detected:
decision:
error detected: imprecision
decision: accept run
1 ctrl value exceeds ±3SDs
1-3s
1-3s
error detected:
imprecision/ systematic bias
range between 2 levels of control with a run exceeds 4SDs
R4s
R4s
error detected:
imprecision
2 consecutive values of 2 qc samples exceed 2SDs same direction
2-2s
2-2s
error detected:
bias (inaccuracy)
4 consecutive control values exceed 1SD
4-1s
10 consecutive values same side of the mean
10x̄
4-1s and 10x̄
error detected:
bias trend
what to do during 1-3s, R4s, 2-2s, 4-1s and 10x̄
reject run
troubleshoot
rerun
when in ctrl -> release result
8 consecutive values exceed 1SD same direction
8-1sc
cumulative sum of SDI
CUSUM
exponentially weighted moving average
EWMA
2 out of 3 control values exceed the same mean ±2SDs
2 of 3-2s
3 consecutive control exceed same mean ±1SD
3-1s
6 consecutive control values are on the same side of the mean
6x̄
8-1s, CUSUM, EWMA
error detected:
decision:
bias trend
reject run
2 of 3-2s, 3-1s, 6x̄
error detected:
decision:
3 levels of control: REJECT RUN
