For quantitative investigations of deformed materials using the electron back scatter pattern (EBSP) technique, the angular resolution limit of the technique, resulting in an 'orientation noise' superimposed on the measurements, still presents many problems. In order to better understand EBSP data, particularly on highly deformed samples, it is necessary to quantify the extent of the orientation noise. However unlike the case of single crystals, it is not possible to directly measure the orientation noise. Some techniques are suggested for estimating the orientation noise level for deformed samples, and examples given of cases where a quantitative knowledge of the orientation noise level can be used to assist in the design and interpretation of EBSP experiments of deformed samples.