Hi all . I have a question, that is very important for me!

It is written in book "basic statistics for business and economics" for organizing data into a frequency distribution:

step 1: Decide on the number of classes. The goal is to use just enough groupings or classes to reveal the shape of the distribution. Some judgment is needed here. A useful recipe to determine the number of classes (k) is the "2 to the k rule". This guide suggests you select the smallest number (k) for the number of classes such that 2^{k}(in words, 2 raised to the power of k) is greater than the number of observations (n). [n<=2^{k}]

I want to know, how can I prove this formula?

Please Help!