Abstract: The background value and anomaly threshold of soil radon concentration in the investigation area were calculated by using four methods which include: traditional statistical method, distribution form test method, exploratory data analysis method and median absolute dispersion method. The robustness of the four methods was analyzed. Finally the soil radon concentration level in the investigation area was calculated. The results showed that the soil radon samples in the whole investigation area obeyed an approximate lognormal distribution. The median absolute dispersion method had good robustness in measuring the background value and anomaly threshold of soil radon concentration. The background value of soil radon concentration in the whole region was 9 132 Bq/m³, and the anomaly threshold was 13 497 Bq/m³.

Key words: Soil radon concentration, Survey scale, Statistical method, Median absolute dispersion method