Traditionally, the least-squares method is applied to separate the highly radioactive zones of gamma-ray
spectrometric maps in order to find the normal radioactive background of the host rocks. In the present
study, the regional background of gamma-ray spectrometric data was calculated by using the median
instead of least-squares method which is based on the mean. The obtained least-squares do not properly fit
due to the strong effect of the few outlier data points that are extremely high or low. The median is less
affected by outliers and skewed data. If we reject these anomalous zones data, the proper fitting takes place.
This study deals with using the median as a more suitable measure of central tendency for data classified on
an ordinal scale. The mean is not suitable when the data include exceptionally high or low values because
these have great influence on the outcome. The median was applied to the gamma-ray spectrometric (Total
Count) survey data of El-Missikkat-Gidami area to separate the radioactive anomalous zones from the
normal radiation of the host rocks.