Indefiniteness of result due to finite precision of experiment. Measure of fluctuation in result upon repeated experimentation.

An unsystematic error; a quantity (often indirectly observed) that appears to have no relationship with any other variable. Related to reliability and the standard error of measurement. American Educational Research Association, American Psychological Association, & National Council on Measurement in Education. (1999). Standards for educational and psychological testing. Washington, DC: American Educational Research Association, p. 180.

The difference between the actual and the desired quantity that varies randomly; that is, if a probability distribution of differences is produced, it is the Gaussian error function.

A source of error that limits the precision of a measurement. An error that is equally likely to give results that are too large or too small. See systematic error.

error that occurs as a result of sampling variability, through no direct fault of the sampler. It is a reflection of the fact that the sample is smaller than the population; for larger samples, the random error is smaller.

A wrong result due to chance. Unknown sources of variation are equally likely to distort the result in any direction.

Error that occurs due to natural variation in the process. Note: Random error is typically assumed to be normally distributed with zero mean and a constant variance. Note: Random error is also called experimental error.

measurement error that arises when you are not interviewing all the members of a study group or control group. Differences between the pre-survey and post-survey may show change in certain questions that appears to be a real change in the group being measured, but may turn out to be a function of having interviewed group members atypical of the full group. Random error is captured mathematically in the confidence interval.

a result of a measurement minus the mean that would result from an infinite number of measurements of the same measurand carried out under repeatability conditions.

an error which is present every time you take the measurement, but which varies unpredictably in size and direction

Error governed by chance. (See also Bias)

Error that is not systematic in nature, i.e., that which is due to unpredictable fluctuations in the accuracy of observation.

Unexplainable but characterizable variations in repeated measurements of a fixed true value resulting from processes that are random or statistically independent of each other, such as imperfections in measurement techniques. Some random errors could be reduced by developing improved techniques.

measurement error due to changing aspects of the respondent or measurement situation.

an error that has an equal probability of being high or low.

The inherent imprecision of a given process of measurement, the unpredictable component of repeated independent measurements of the same object under sensibly uniform conditions.

Normal variation in measurements. The natural variation within a measurement process that causes measured values to deviate from each other to some degree. Repetitive measurements that consist of only random errors (no bias errors) will usually form a normal (Gaussian or bell-shaped) distribution around the true value.

indeterminate error. Compare with systematic error, gross error and mistake. Random errors are errors that affect the precision of a set of measurements. Random error scatters measurements above and below the mean, with small random errors being more likely than large ones.

Variations of repeated measurements that are random in nature and not predictable individually. The causes of random error are assumed to be indeterminate or non-assignable. The distribution of random errors is assumed generally to be normal (Gaussian).

Deviations from the "true value" can be equally likely to be higher or lower than the true value. See Systematic Error.

Error that affects measurement in a transient, inconsistent manner.