STATISTICAL CONCEPTS in QUALITY CONTROL

A statement of the extent of random variation in any series of measurement

A measure of the distribution of values around the mean

Square of the standard deviation

Used to detect significant differences between groups of data

Determine contributions of various factors to the total variation

Percentile expression of the mean

Measure of the relative magnitude of variability

CV = s (100)/X

Reported values do not fall along the line of slope when graphed

Reported lab results do not correspond to the correct value

Problem on Accuracy (Bias) = ____________

Refers to laboratory analyses that are subject to imprecision

Problem on Precision (CV) = _____________

can be systematic or personnel-related

Sources cannot be completely controlled or identified

Increase the extent of variability of results

Displace the mean value on one direction (may be up or down), but do NOT affect the overall variability as shown by the SD value

decomposition of reagents during storage

Series of values on the control chart that continue to increase or decrease for at least a period of six (6) consecutive days

Values that distribute themselves on one side of the mean for at least six (6) consecutive days

Q.C. procedures performed on a daily basis within individual laboratories

Monitoring is carried out using:

Performed on a less frequent basis (e.g. 3x a year) to compare performance b/w or among laboratories

graphical representations that display the control observation as a function or time