1. A method for identifying artifacts in optical measurements conducted for the purpose of determination of the concentration of an analyte in a tissue, the method comprising the steps of: (a) providing an apparatus for measuring at least one optical property of the tissue; (b) introducing electromagnetic radiation at at least one wavelength into the tissue by means of the apparatus; (c) collecting optical data from the tissue over a selected period of time; (d) introducing the collected data into an algorithm to identify an artifact in the data, the artifact resulting from movement of the probe or the tissue during a brief period of time; and (e) determining whether an artifact has appeared in the data.