Statistics, Quality Assurance, and Quality Control Vocabulary

Vocabulary flashcards covering key terms from the lecture notes on Statistics, Quality Assurance, and Quality Control.

Quality Assurance

Broad spectrum of plans, policies, and procedures which provide for the achievement of quality goals in the laboratory. These quality goals are designed to detect, control, and prevent the occurrence of errors. Used to measure and monitor quality laboratory processes.

Quality Control

Quantitative techniques and procedures which monitor performance parameters, such as the sources of error and the magnitude of these errors. Used to measure and monitor quality laboratory processes through the use of materials processed along with patient specimens to determine whether patient results may be deemed reliable.

Accuracy

The measure of the correctness of a result; how close the result comes to a true value.

Precision

A measure of reproducibility; the measure of the variability present in an analytical process.

Random error

Those errors which occur without prediction or regularity.

Systematic error

Those errors which occur within the test system or methodology that occur regularly.

Proportional systematic error

Those errors that are proportional to analyte concentration.

Constant systematic error

Those errors which are constant or in the same amount over the entire range of analyte concentration.

Standard

A sample of known concentration that is used to calibrate or set an instrument's parameters.

Control

A sample with a range of concentrations either determined by the manufacturer (assayed control) or determined by the particular laboratory (unassayed control).

Statistics

A field of study concerned with organization and summarization of data and drawing inferences about a body of data when only part of the data is observed.

Descriptive statistics

Used to summarize the important features of a group of data; concerned with the mean, range, variability, and distribution of a data set.

Gaussian (Normal) distribution

A bell-shaped distribution that appears with enough data points.

Mean

Center of distribution determined from the sum of the values divided by the number of values; represented as x and reported in the same units as the test. It describes the central tendency of the population only if the histogram is symmetric about the mean.

Mode

Most frequently obtained value.

Median

The value in the middle of the distribution; half the values are greater and half are smaller. If even in number, average the middle two values.

Range

The difference between the highest and lowest values in a set.

Variance

a measure of the average squared distance of data points from the mean

Standard Deviation

describes the spread of data about the mean. In the clinical laboratory, SD determines if any values deviate significantly from the mean. Reported in the same units as the data

Coefficient of Variation

the size of the standard deviation in relationship to the mean. It is expressed as a percent so is dependent on the units. Is useful to compare deviations of different pools and different data. Interpreted as the smaller percentage, the less the deviation. It is reported in percentage units

Confidence Limit/Interval

limits between which a specified proportion of a population is expected to lie