Dear UQLab Team,

I use Sobol’ sensitivity indices for my model and obtain that I have zero first-order Sobol’ indices for all input parameters but high second-order Sobol’ indices which constitute most of the Total Sobol’s indices. As much as I read, the first order Sobol’ indices constitute most of the Total Sobol’s indices.

My question is: Is it usual that in some models the first-order indices can be zero, and the impact of the interaction of input parameters can be higher than the individual effect of each parameter? If yes, How do I have to interpret my results? Because I know that my input parameters are independent. So, there is no single effect but some indirect relation between my input parameters on output results?

Thanks in advance