Thanks a lot Habib ji. But I know how to calculate standard error from the observed data by using the basic part of statistics that is mentioned in the link you provided. My question was something related to tree growth equation/ model where contant parameters (say, a, b, c, d, etc.) are also needed to be calculated for standard error.
Thanks Bruno Martin... But can you guide me how to remove the tag C++. I did not include it. It has automatically added. But do not know about this tag.