After looking at the picture in the Histogram page, I was getting concerned about the first bin on the left, which was basically saying that 8% of the readings had a value less than 0.049 μSv/h.
I wanted to achieve a better characterization of the histogram in that region, so I pre-processed (decimated) the original data, which was given as one sample every 10 seconds, to obtain one sample every minute, leading to a 6-fold improvement in the bin width (narrower is more precise). I fed that data to my plotting procedure and the results is the following picture:
One comment about this picture is that it could possibly explain why my readings are about 3 times higher than what is reported by the official sources: I am reporting the average value of the distribution, and maybe the other sources are reporting the minimum value, which in my picture lies at about 0.049 μSv/h.
Another interpretation could be given by observing that the general envelope shape is not entirely like a bell shape, but it has some small “bumps”, specifically one on the left at 0.049 μSv/h, and a couple on the right above 0.211 μSv/h. Assuming that each partial bell shape is due to a separate stochastic process, we can identify three contributes to the picture:
- I can explain the bumps on the right as caused by electrical interference in the measuring instrument (I know for sure that I need to provide better electrical shielding to my measuring instrument).
- Arguably the little bump at 0.049 μSv/h is what everybody else is measuring and reporting.
- Now the question is: what is the cause for the main bell shape ? For the time being I will assume that it is indeed the gamma radiation that I am intending to measure.