Variation of output data from Radiance-measure

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I'm actually working with Radiance measure in OpenStudio (V 1.14).

I just realize that if I run the same model, three time for example, there are fluctuations from Illuminance points data in the map.ill file. First, I try different models and different Weather files but I got the same problem.

There is an example of the fluctuation for 3 simulations.

Time    Sim. 1 (Lux)    Sim. 2 (Lux)    Sim. 3 (Lux)    Variation (Lux)
8:00      15981          15907.6          16041.5         133.9
9:00      21595          21754.4           21698          159.4
10:00     24567          24767.6          24721.5         200.6
11:00     21870.1        21983.2          22302.8         432.7
12:00     11636.3         11432           11490.5         204.3
13:00     4564.3           4608            4567.9          43.7
14:00     3273.3          3242.7           3267.2          30.6
15:00     2175.4          2155.4           2178.5          23.1

Since the parameters of the model are the same, is the variation of the results are made by Radiance measure calculations?

Do you have any suggestions?