1. A method for reducing noise effects in a system for measuring a physiological parameter, the method comprising the steps of: generating a plurality of measurements derived from at least one wavelength of electromagnetic energy transmitted through living tissue; comparing selected measurements with at least one expected measurement characteristic; assigning one of a plurality of variable weights to each selected measurement based on the comparing step thereby generating a plurality of differently weighted measurements, the variable weights being assigned, in part, in response to a similarity between each selected measurement and a corresponding previous measurement, the variable weights comprising a plurality of different non-zero numbers; and averaging a plurality of the differently weighted measurements to obtain a filtered measurement for use in estimating the physiological parameter.