Statistical Artifact
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In
natural science Natural science is one of the branches of science concerned with the description, understanding and prediction of natural phenomena, based on empirical evidence from observation and experimentation. Mechanisms such as peer review and repeatab ...
and signal processing, an artifact or artefact is any error in the perception or representation of any information introduced by the involved equipment or technique(s).


Computer science

In '' computer science'', digital artifacts are anomalies introduced into digital signals as a result of
digital signal processing Digital signal processing (DSP) is the use of digital processing, such as by computers or more specialized digital signal processors, to perform a wide variety of signal processing operations. The digital signals processed in this manner are ...
.


Microscopy

In ''
microscopy Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of micr ...
'', visual artifacts are sometimes introduced during the processing of samples into
slide Slide or Slides may refer to: Places *Slide, California, former name of Fortuna, California Arts, entertainment, and media Music Albums * ''Slide'' (Lisa Germano album), 1998 * ''Slide'' (George Clanton album), 2018 *''Slide'', by Patrick Glees ...
form.


Econometrics

In '' econometrics'', which trades on computing relationships between related variables, an artifact is a spurious finding, such as one based on either a faulty choice of variables or an over-extension of the computed relationship. Such an artifact may be called a ''statistical artifact''. For instance, imagine a hypothetical finding that presidential approval rating is approximately equal to twice the percentage of citizens making more than $50,000 annually; if 60% of citizens make more than $50,000 annually, this would predict that the approval rating will be 120%. This prediction is a statistical artifact, since it is spurious to use the model when the percentage of citizens making over $50,000 is so high, and gross error to predict an approval rating greater than 100%.


Remote sensing


Medical imaging

In
medical imaging Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues (physiology). Medical imaging seeks to rev ...
, artifacts are misrepresentations of tissue structures produced by imaging techniques such as ultrasound, X-ray,
CT scan A computed tomography scan (CT scan; formerly called computed axial tomography scan or CAT scan) is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers ...
, and
magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...
(MRI). These artifacts may be caused by a variety of phenomena such as the underlying physics of the energy-tissue interaction as between ultrasound and air, susceptibility artifacts, data acquisition errors (such as patient motion), or a reconstruction algorithm's inability to represent the anatomy. Physicians typically learn to recognize some of these artifacts to avoid mistaking them for actual pathology. In ultrasound imaging, several assumptions are made from the computer system to interpret the returning echoes. These are: echoes originate only from the main ultrasound beam (while there are side lobes and grating lobes apart from the main ultrasound beam); echoes returns to transducer after a single reflection (while an echo can be reflected several times before reaching the transducer); depth of an object relates directly to the amount of time for an echo to reach the transducer (while an echo may reflect several times, delaying the time for the echo return to the transducer); speed of ultrasound in human tissue is constant, echoes travel in a straight path. and acoustic energy of an echo is uniformly attenuated. When these assumptions are not maintained, artifacts occur.


Medical electrophysiological monitoring

In medical electrophysiological monitoring, artifacts are anomalous (interfering) signals that originate from some source other than the electrophysiological structure being studied. These artifact signals may stem from, but are not limited to: light sources; monitoring equipment issues; utility frequency (50 Hz and 60 Hz); or undesired electrophysiological signals such as EMG presenting on an EEG-, EP-, ECG-, or
EOG Electrooculography (EOG) is a technique for measuring the corneo-retinal standing potential that exists between the front and the back of the human eye. The resulting signal is called the electrooculogram. Primary applications are in ophthalmol ...
- signal. Offending artifacts may obscure, distort, or completely misrepresent the true underlying electrophysiological signal sought.


Radar

In radar signal processing, some echoes can be related to fixed objects (
clutter Clutter and its derivations may refer to any of the following: Excessive physical disorder * Clutter, a confusing, or disorderly, state or collection, and possible symptom of compulsive hoarding * Clutter (marketing), numerous advertisements, ...
), multipath returns, jamming, atmospheric effect ( brightband or attenuation), anomalous propagation, and many other effects. All those echoes must be filtered in order to obtain the position, velocity and type of the real targets that may include aircraft, and weather.


See also

* Sonic artifact, in sound and music production, sonic material that is accidental or unwanted, resulting from the editing of another sound. * Visual artifact, in imaging, any unwanted visual alteration introduced by the imaging equipment. *
Compression artifact A compression artifact (or artefact) is a noticeable distortion of media (including images, audio, and video) caused by the application of lossy compression. Lossy data compression involves discarding some of the media's data so that it beco ...
, in computer graphics, distortion of media by the data compression.


References

{{DEFAULTSORT:Artifact (Error) Error Optical illusions Data compression Radar theory