Laboratory statistics

Question 1

Average or arithmetic mean of a data set

Answer 1

Mean (𝒙̅)

Question 2

Midpoint of a data set after rank-ordering the values

Answer 2

Median

Question 3

Most frequently occurring value in a data set

Answer 3

Mode

Question 4

Formula for standard deviation

Answer 4

Standard deviation (s) is the square root of variance.

Question 5

Term for the square of the standard deviation

Answer 5

Variance (s²)

Question 6

Best indicator of precision in a data set

Answer 6

Coefficient of Variation, which should be <10%.

Question 7

Difference between the highest and lowest values in a data set

Answer 7

Range

Question 8

In a Gaussian/Normal distribution, how are data points distributed?

Answer 8

Symmetrically around the mean in a bell-shaped curve.

Question 9

In a Gaussian distribution, what are the relationships between the mean, median, and mode?

Answer 9

They are identical.

Question 10

Rule that describes the distribution of data points in a normal distribution

Answer 10

Empirical rule: 68% ±1s, 95% ±2s, 99.7% ±3s.

Question 11

Pair of medical decision points that span the limits of results expected for a healthy population.

Answer 11

Reference interval

Question 12

Requires at least 20 study individuals; adopted if <10% (1-2 out of 20) fall outside the range.

Answer 12

Verifying a reference interval

Question 13

Establishing a reference interval required number of study individuals

Answer 13

At least 120

Question 14

Reference interval establishment should have a confidence interval of:

Answer 14

0.95

Question 15

First step in method evaluation; usually done by running two control materials twice a day over a 10-day period.

Answer 15

Precision study

Question 16

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.

Answer 16

Recovery study

Question 17

Compares the means of two groups of data or the accuracy of two methods.

Answer 17

t test

Question 18

Compares the SD of two groups of data or the precision of two procedures.

Answer 18

F test

Question 19

Used to compare two methods using the best fit line through the data points.

Answer 19

Linear regression

Question 20

Independent variable/ref method in linear regression.

Answer 20

x (VOYD)

Question 21

Dependent variable/new method in linear regression.

Answer 21

y (VOYD)

Question 22

Ability of a method to detect the smallest concentration of an analyte.

Answer 22

Analytical sensitivity (screening test)

Question 23

Ability of a method to detect only the analyte of interest.

Answer 23

Analytical specificity (confirmatory)

Question 24

Ability of a test to detect a given disease or condition; proportion of individuals with the disease who have a positive test result.

Answer 24

Diagnostic sensitivity

Question 25

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.

Answer 25

Diagnostic specificity

Question 26

Probability that a positive test result indicates disease; proportion of individuals with a positive result who truly have the disease.

Answer 26

Positive predictive value

Question 27

Probability that a negative test result indicates absence of disease; proportion of individuals with a negative result who truly do not have the disease.

Answer 27

Negative predictive value