In natural science and signal processing, an artifact 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 processing.
Microscopy
In microscopy, artifacts are sometimes introduced during the processing of samples into slide form. See Artifact (microscopy)
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, artifacts are misrepresentations of tissue structures seen in medical images produced by modalities such as Ultrasonography, X-ray Computed Tomography, and Magnetic Resonance Imaging. These artifacts may be caused by a variety of phenomena such as the underlying physics of the energy-tissue interaction (i.e. Ultrasound-air), 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.
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- 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 fix targets (clutter), 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 (aircraft, weather, etc...)