Systematic errors are biases in measurement which lead to measured values being systematically too high or too low. Bias is a term used to describe a Tendency or Preference towards a particular perspective, Ideology or result especially when the tendency interferes Measurement is the process of estimating the magnitude of some attribute of an object such as its length or weight relative to some standard ( unit of measurement) such as See also biased sample and errors and residuals in statistics. A biased sample is a statistical sample of a population in which some members of the population are less likely to be included than others In Statistics and optimization, the concepts of statistical error and residual are easily confused with each other All measurements are prone to systematic error. A systematic error is any biasing effect, in the environment, methods of observation or instruments used, which introduces error into an experiment and is such that it always affects the results of an experiment in the same direction. Vicinty redirects here Vicinity Corporation provided the MapBlast web mapping service in the late 1990s Observation is either an activity of a living being (such as a Human) which senses and assimilates the Knowledge of a Phenomenon, or the recording of data The word error has different meanings and usages relative to how it is conceptually applied In scientific inquiry an experiment ( Latin: Ex- periri, "to try out" is a method of investigating particular types of research questions or Distance measured by radar will be in error if the slight slowing down of the waves in air is not accounted for. Distance is a numerical description of how far apart objects are Radar is a system that uses electromagnetic waves to identify the range altitude direction or speed of both moving and fixed objects such as Aircraft, ships The oscillation frequency of a pendulum will be in error if slight movement of the support is not accounted for. A pendulum is a mass that is attached to a pivot from which it can swing freely Incorrect zeroing of an instrument leading to a zero error is an example of systematic error in instrumentation. So is a clock running fast or slow. Circadian Locomotor Output Cycles Kaput, or Clock is a gene which encodes proteins regulating Circadian rhythm. See also observational error and errors and residuals in statistics. Observational error is the difference between a measured value of quantity and its true value In Statistics and optimization, the concepts of statistical error and residual are easily confused with each other

Constant systematic errors are very difficult to deal with, because their effects are only observable if they can be removed. Such errors cannot be removed by repeating measurements or averaging large numbers of results. A common means to remove systematic error is the observation of a known process, i. e. through calibration. Calibration is the process of establishing the relationship between a measuring device and the units of measure Another means to remove systematic error is by a subsequent measurement with a more sophisticated experiment equipment.

## Drift

Systematic errors which change during an experiment (drift) are easier to detect. Measurements show trends with time rather than varying randomly about a mean. In Statistics, mean has two related meanings the Arithmetic mean (and is distinguished from the Geometric mean or Harmonic mean

Drift is evident if a measurement of a constant quantity is repeated several times and the measurements drift one way during the experiment, for example if each measurement is higher than the previous measurement which could perhaps occur if an instrument becomes warmer during the experiment. If the measured quantity is variable, it is possible to detect a drift by checking the zero reading during the experiment as well as at the start of the experiment (indeed, the zero reading is a measurement of a constant quantity). If the zero reading is consistently above or below zero, a systematic error is present. If this cannot be eliminated, for instance by resetting the instrument immediately before the experiment, it needs to be allowed for by subtracting its (possibly time-varying) value from the readings, and by taking it into account in assessing the accuracy of the measurement.

If no pattern in a series of repeated measurements is evident, the presence of fixed systematic errors can only be found if the measurements are checked, either by measuring a known quantity or by comparing the readings with readings made using a different apparatus, known to be more accurate. For example, suppose the timing of a pendulum using an accurate stopwatch several times gives readings randomly distributed about the mean. A stopwatch is a handheld Timepiece designed to measure the amount of time elapsed from a particular time when activated to when the piece is deactivated A systematic error is present if the stopwatch is checked against the 'speaking clock' of the telephone system and found to be running slow or fast. A speaking clock service is used by people who wish to know the correct and accurate Time. Clearly, the pendulum timings need to be corrected according to how fast or slow the stopwatch was found to be running. Measuring instruments such as ammeters and voltmeters need to be checked periodically against known standards. An ammeter is a Measuring instrument used to measure the Electric current in a circuit. A voltmeter is an instrument used for measuring the Electrical potential difference between two points in an electric circuit

Systematic errors can also be detected by measuring already known quantities. For example, a spectrometer fitted with a diffraction grating may be checked by using it to measure the wavelength of the D-lines of the sodium electromagnetic spectrum which are at 589. A spectrometer is an Optical instrument used to measure properties of Light over a specific portion of the Electromagnetic spectrum, typically used In Optics, a Diffraction grating is an optical component with a regular pattern which splits ( diffracts) light into several beams travelling in different In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies 0 and 589. 6 nm. The measurements may be used to determine the number of lines per millimetre of the diffraction grating, which can then be used to measure the wavelength of any other spectral line. The Millimetre ( American spelling: millimeter, symbol mm) is a unit of Length in the Metric system, equal to