Laboratory Statistics Flashcards
Measures of Center
Mean, Median, Mode
Measures of spread
SD, Cv, Range
Average or arithmetic mean
Mean
Midpoint of a data set after the values have been rank-ordered
Median
Most frequently occurring value in a data set
Mode
Distribution of data points around the mean
SD (Standard Deviation)
Best indicator of precision
CV (Coefficient of Variation)
Difference between the highest and lowest values
Range
Data points are distributed symmetrically around the mean (bell-shaped curve) with most values close to the center
Gaussian/Normal Distribution
Done to confirm the validity of an existing or published RI for an analyte
Verifying a reference interval
How many study individuals and what percent is needed for the RI to be adopted in verifying a reference interval?
20; less than or equal to 10%
Done when there is no exisiting RI for an analyte or when the transference studies fail
Establishing a reference interval
How many study individuals and what percent confidence interval is base for the RI in establishing a reference interval?
120; 95%
First step in method evaluation; usually done by running 2 control materials twice a day for a period of 10 days
Precision study
Involves spiking a sample with a known amount of an analyte and determining how much of it can be detected by the method in the presence of other compounds in the matrix
Recovery study
Compares the means of two groups o data or the accuracy of two methods
T test
Compares the SD of two groups of data or the precision of two procedures
F test
Used to compare two methods using the best fit line through the data points
Linear regression
Ability of a method to detect the smallest concentration of an analyte
Analytical sensitivity
Ability of a method to detect only the analyte of interest
Analytical specificity
Ability of a test to detect a given disease or condition; proportion of individuals with the disease who have a positive test result
Diagnostic sensitivity
Ability of a test to detect the absence of a given disease or condition; proportion of individuals with no disease who have a negative test result
Diagnostic specificity
Probability that a positive test result indicates disease; proportion of individuals with a positive result who truly have the disease
Positive predictive value
Probability that a negative test result indicates absence of disease; proportion of individuals with a result who truly do not have the disease
Negative predictive value
