Eifclusive method—In this method, series are so fomed that the upper limit of one class interval is t% lower limit of the next class interval. Here the upper limit ot (rr\e class interval is equal to the lower limit 6f its next class interval. Inclusive Method— In this method, safes are so formed that lower limit ana me’upper limit of a class interval are included in the class itself. Here the upper limit of one class interval is not ec to the lower limit of its next class interval