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Glossary “M” Definition of Terms in DataMyte


An array of data arranged in rows and columns. Mean (of a population) (µ) — The true arithmetic average of all elements in a population. x approximates the true value of the population mean.

Mean (of a statistical sample) (y) 

The arithmetic average value of some variable. The mean is given by the formula, where x is the value of each measurement in the sample. All x’s are added together and divided by the number of elements (n) in the sample.

Mean Formula

Measurement Accuracy

The extent to which the average result of a repeated measurement tends toward the true value of the measured quantity. The difference between the true value and the average measured value is called the instrument bias, and may be due to such things as improper zero-adjustment, nonlinear instrument response, or even improper use of the instrument. 

Measurement Error

The difference between the actual value and the measured value of a measured quantity. 

Measurement Precision

The extent to which a repeated measurement gives the same result. Variations may arise from the inherent capabilities of the instrument, from variations of the operator’s use of the instrument, from changes in operating conditions, etc. 

Median (of a statistical sample)

For a sample of a specific variable, the median is the point X, where half the sample elements are below X, and half above X.

Median Chart

For variables data: a control chart of the median of subgroups. Metrology — The science of measurement.


See ANSI/ASQC Z1.4-1993. 


 A set of government specifications for acceptance sampling plans based on acceptable quality level (AQL) for variables data, using the assumption that the variable is normally distributed.


A set of standard government requirements for soldered electrical and electronic assemblies. Standards address design, production, process control, and inspection of these assemblies. 


A combination of two distinct populations. On control charts, a mixture is indicated by an absence of points near the centerline. 

Mode (of a statistical sample)

The most frequently-occurring value of the sample variable. 

Modified Control Limits

Control limits calculated from information other than the process’s statistical variation, such as tolerances. Must be used cautiously, because the process could be working within its normal variation, but show up on the control chart as out of control when limits do not account for that variation. 

Monte Carlo Simulation

A computer modeling technique to predict the behavior of a system from the known random behaviors and interactions of the system’s component parts. A mathematical model of the system is constructed in the computer program, and the response of the model to various operating parameters, conditions, etc. can then be investigated. The technique is useful for handling systems too complex for analytical calculation. 

Moving Average Moving Range Charts

A control chart that combines rational subgroups of data and plots the combined subgroup averages and ranges. Often used in continuous process industries, such as chemical processing, where single samples are analyzed. 

MTBF (Mean Time Between Failures)

Mean time between successive failures of a repairable product. This is a measure of product reliability. 


An electrical switching device that allows the transmission of two or more signals on the same circuit. DataMyte multiplexers can be used with a wide variety and type of digital and analog gauges.

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