Identifying Bin Metrics from Parametric Distribution Analysis

Hi,

   I've constructed a series of parametric distributions consisting of y values that are "counts" and x values that correspond to mean values of the specified "bins".  In my case these bins correspond to ranges of chemical concentration.   
   Ultimately I would like to analyze these parametric distributions in terms of mean, median, and potentially moments.   
   I have run into a problem in that it seems the Matlab distribution analysis functions provide these metrics only for the y values, for example mean count. I am more interested in interpreting these metrics for x values, for example to identify the mean bin/ concentration associated with the mean count rather than the mean count alone.  
   Can somebody please provide some tips for analyzing these distributions?

Thanks so much,

Avi