BASIC QUALITY CONTROL STATISTICS

Question 1

The mean (or average) is the laboratory’s best estimate of the
analyte’s true value for a specific level of control.

Answer 1

Mean

Question 2

Standard deviation quantifies how close numerical values are
in relation to each other

Answer 2

Standard deviation

Question 3

implies that data points are close to the mean

Answer 3

Low SD

Question 4

implies that data points are spread out over a
large range of values

Answer 4

High SD

Question 5

A graph of all the quality control results in a month

Answer 5

Levey Jennings Chart

Question 6

In levey jenning → in a month, minimum of ____controls should be run

Answer 6

20

Question 7

→ concentrations

Answer 7

Y axis

Question 8

line in the middle

Answer 8

Mean

Question 9

→ days or number of run

Answer 9

X axis

Question 10

→ exactly ___ runs of control in a day (per shift)

Answer 10

3

Question 11

__________ is a measure of variability

Answer 11

Coefficient of variation

Question 12

A method or instrument’s _______ is expressed as a percent

Answer 12

Coefficient of variation

Question 13

A statistic that measures your lab’s bias relative to your
consensus group. An estimate of reliability

Answer 13

Standard deviation index

Question 14

→ Ideal score; Identical to peer group
→ data values of the lab are in 100% agreement with the
reference method

Answer 14

SDI - 0

Question 15

→ acceptable to marginal performance
→ may need to investigate test system bias

Answer 15

SDI -1 -1.5

Question 16

→ marginal performance
→ may need to perform corrective action

Answer 16

1.5-2.0

Question 17

A statistic that compares your lab’s precision to that of other
labs in a consensus group.

Answer 17

Coefficient variation of ratio

Question 18

→ Acceptable performance
→ Indicates that precision is better than peer group

Answer 18

Less than 1 - CVR

Question 19

→ Acceptable to marginal performance
→ May need to investigates test system imprecision

Answer 19

1 to 1.5 - CVR

Question 20

→ Marginal performance
→ May need to perform corrective action

Answer 20

1.5-2.0 - CVR

Question 21

Is defined as abrupt changes in the control values

Answer 21

Shift

Question 22

→ if there is 6 or more consecutive QC results already fall in
the one side of the mean → reject results

Answer 22

Shift

Question 23

● Shifts in QC data represent a sudden and dramatic positive or
negative change in test system performance

Answer 23

Shift

Question 24

Sudden failure or change in the light source

Answer 24

Shift

Question 25

Change in reagent formulation

Answer 25

Shift

Question 26

Change of reagent lot

Answer 26

Shift

Question 27

Major instrument maintenance

Answer 27

Shift

Question 28

Sudden change in incubation temperature (enzymes only)

Answer 28

Shift

Question 29

● Change in room temp. or humidity

Answer 29

Shift

Question 30

Failure in sampling system & reagent dispense system

Answer 30

Shift

Question 31

Inaccurate calibration/recalibration

Answer 31

Shift

Question 32

Indicated a gradual loss of reliability in the test system

Answer 32

Trend

Question 33

→ if there is 6 or more consecutive QC results that slowly but continually move in one direction → data values are seen on one side of the mean → reject results

Answer 33

Trend

Question 34

Deterioration of the instrument light source

Answer 34

Trend

Question 35

Gradual accumulation of debris in sample/reagent tubing

Answer 35

Trend

Question 36

Gradual accumulation of debris on electrode surfaces

Answer 36

Trend

Question 37

Aging of reagents

Answer 37

Trend

Question 38

Gradual deterioration of control materials

Answer 38

Trend

Question 39

Gradual deterioration of incubator chamber temp.

Answer 39

Trend

Question 40

Gradual deterioration of light filter integrity

Answer 40

Trend

Question 41

Gradual deterioration of calibration

Answer 41

Trend

Question 42

→ a trend or shift away from the laboratory mean

Answer 42

Systematic error

Question 43

→ not acceptable; indicates that there are errors in the system

Answer 43

Systematic error

Question 44

any random deviation away from the laboratory mean

Answer 44

random error

Question 45

variations on QC results that shows no pattern

Answer 45

random error

Question 46

does not reflect failure on some parts of the testing system

Answer 46

random error

Question 47

→ not likely to reoccur

Answer 47

random error

Question 48

→ rejected if the data value that showed the random error exceeds ± 2SD

Answer 48

random error

Question 49

If 2 levels of controls

Answer 49

Westgard multirule system

Question 50

● a “multi-rule” system developed by _________ based on statistical concepts

Answer 50

Dr. James O. Westgard

Question 51

a combination of decision criteria or rules to assess if a system is in-control

Answer 51

Westgard multirule system

Question 52

● use when at least 2 levels of control are run with the examination run

Answer 52

Westgard multirule system

Question 53

● cannot use with only one control

Answer 53

Westgard multirule system

Question 54

This is a warning rule that is violated when a single control observation is outside the ± 2s limits.

Answer 54

12s rule

Question 55

Two consecutive controls exceed the mean by +/- 2SD

Answer 55

22s rule

Question 56

4 consecutive controls on one side of the mean exceeds +/-1SD

Answer 56

41s rule

Question 57

10 consecutive controls on one side of the mean

Answer 57

10x rule

Question 58

Improper alignment of sample or reagent pipettes resulting in change in reagent and calibrator volume.

Answer 58

Systematic error

Question 59

● Drift or shift in incubator chamber temperature, deterioration of photometric light source

Answer 59

Systematic error

Question 60

● Change of calibration/reagent lot

Answer 60

Systematic error

Question 61

● Deterioration of reagent/calibrator/control product while in use, storage or shipment

Answer 61

Systematic error

Question 62

● Incorrect handling of control product

Answer 62

Systematic error

Question 63

Inadequate storage of reagent or calibrators/control products

Answer 63

Systematic error

Question 64

Change in test operator

Answer 64

Systematic error

Question 65

Any QC result outside ± 3s violates this rule.

Answer 65

13s rule

Question 66

If there is at least a 4s difference between control values within a single run, the rule is violated for random error.

Answer 66

R4s rule

Question 67

Power Supply

Answer 67

Random error

Question 68

Double pipetting of control sample

Answer 68

Random error

Question 69

Misplacement of Control sample within the run

Answer 69

Random error

Question 70

Random air bubbles in reagent or sample pipette system

Answer 70

Random error

Question 71

Incorrect reconstitution of the control product

Answer 71

Random error

Question 72

Inappropriate Storage of control

Answer 72

Random error

Question 73

Inadequately mixed reagents

Answer 73

Random error

Question 74

Individual operator variation in pipetting , timing , etc.

Answer 74

RAndom error