MIDTERM Flashcards
STATISCAL TOOLS
Mean
Median
Mode
Range
Standard deviation
Variance
Coefficient of variation
determine the concentration of an unknown sample
Reference calibration curve
calculate the limit of detection, and the limit of quantitation.
Reference calibration curve
Measure of the center of Distribution
Mean
the sum of the observed values, from the first through the last
Sum of X
Total number of observations
N
values are arranged in increasing order
Median
the value of the measured variables below which half the observation fall
- arithmetic mean of the 2 middle observation
- ex. 3,4,5,5,5,6,7
Median
value that occurs most frequently in a list of items of data.
not affected by extreme values or outliers.
- ex: 3,4,5,5,5,6,7
Mode
difference between the highest and lowest data points.
- ex: 7,6,5,5,5,4,3
Range
measure of the dispersion of values around the mean
Standard deviation
most frequently used measure of dispersion
- denoted by the use of s2
Variance
defined as a sum of the square of the deviation of the observation from the mean divided by the
total number of observations less 1
Variance
expressed as percentage of the mean
Coefficient of variation
applied to activities directed toward the monitoring of the individual elements of care.
Quality control
specimens analyzed for QC purposes.
Quality control materials
- must be available in sufficient quantity to last at least a year and aliquoted in stable form.
Quality control material
- lyophilized for stability, reconstituted in specific diluents
Qc materials
solution that contains a known amount of an analyte
STANDARDS
- Primary
- Secondary
Substance with an assigned value that the manufacturer establishes by using a reference method or by using reference materials traceable to primary stds.
Calibrator
highly purified chemicals that can be measured directly to produce a substance of exact known
concentration.
Primary standard
used for standardization of solutions of unknown strength
Primary standard
stable and can be dried, preferably at 104 - 110 ̊C, without a change in composition;
- not hygroscopic
Primary standard
lower purity with concentration determined by comparison with a primary standard
Secondary standard
certified by the National Bureau of Standards (NBS)
- used as primary standard materials in the clinical laboratory.
- NIST and IRMM
Standard reference materials
chemically and physically similar to the unknown
- specimen and is tested in exactly the same manner.
Control
Monitors PRECISION of the test system
- Results: mean & SD
Control
from either human serum or bovine
Commercial control sera
- Collection of excess non-hemolyzed sera without gross lipemia
Pooled sera
Steps in pooled sera
Centrifuge -> filter -> Analyze at least 20x
Divide into 5 ml each -> stopper and store at -20 ̊C thaw
Disadvantages of pooled sera
deterioration, contamination, loss of potency and pathogenic
Ability of the method to detect even the smallest amount/slight differences in concentration.
Sensitivity
Ability of the method to determine solely the compound it is supposed to measure
Specificity
Indicates how close a measurement is to the true value
Accuracy
Indicates how close test measurements are to each other when the same test is run on the same sample under identical conditions, time after time.
Precision
Ability of a method to maintain its accuracy and precision over an extended period of time
Reliability
Degree to which the method is easily repeated
Practicability
CONTROL: Ideal Characteristic
- Resembles human sample
- Inexpensive and stable for long periods
- Does NOT contain communicable diseases
- No matrix effects
- With known analyte concentrations
- Convenient packaging for easy dispensing and storage
