The invention relates to a method, systems, computer program, and computer-readable medium for reducing artefacts (speckling) which may appear to be noise/errors in a representation of an electrical signal. An Eye Pattern representation of a digital bit stream signal can be used for determining a range of signal quality characteristics, and can be generated from measurements of the proportion of ones and zeroes detected when sampling the signal at both at a reference data sampling position within a bit period and at a range of offset sampling positions. However, the speckling noise which typically exists in such an Eye Pattern reduces the confidence that can be placed in values for different signal characteristics which may be determined from the Eye Pattern. While speckling may be reduced by increasing the sampling frequency used to sample the signal, the present invention reduces speckling by using data gathered at the reference data sampling point to correct data gathered at each of the offset sampling positions. Thereby, the invention reduces the number of samples needed in order to reduce speckling to a particular level.