No measurement is exact, they all contain some degree of errors.
Types of errors:
In experimental observations, an error which does not always recur when an observation is repeated under the same conditions.
A gross mistake caused by carelessness or poor judgement.
e.g. when recording a distance you write 3.01m instead of 3.1m
An error caused by an incomplete element in an instrument.
e.g. backlash in a gear train.
Undetected mistakes that cause a measurement to be very much farther from the mean measurement than other measurements.
The error in initial values used in a computation; especially the error introduced from the previous steps in a step-by-step integration.
An error, usually large, resulting from a human failing or an equipment malfunction.
Variability between observations made at the same values of the independent variable or variables.
Errors that remain after blunders and systematic errors have been removed. They are caused by factors beyond the control of the observers. They tend to be compensating in nature.
e.g. estimating readings on a level rod.
Cumulative errors that can be compensated for, if the errors are known.
e.g. the tape measure being used to make the measurements is incorrect.
Type I Error
Incorrectly rejecting a true null hypothesis.
Type II Error
Not rejecting a false null hypothesis.
See also: Absolute Error, Arithmetic Error, Erratic Error, Error Correction, Error Detector, Gross Error, Inherited Error, Offset Error, Pure Error, Relative Error, Round Off Error, Round-Off Error, Standard Error, Systematic Errors, Truncation Error, Type I Error, Type II Error, Yaw Error.