In the propagation of uncertainty calculations when the uncertainty is derived as the square root of the sum of squares, what implicit assumption is being made regarding the individual contributors?
       |  |       | 1) | They are type A Gaussian distribution |  | 
    |  |       | 2) | They are type B rectangular  distribution |  | 
    |  |       | 3) | They are type B triangular  distribution |  | 
    |  |  | 
    
They are type A Gaussian distribution.
 The individual contributors are assumed as Type A Gaussian distribution.
 In type B evaluation, uncertainity is evaluated through a scientific judgment based on all the available information.