Thus,                                   

Now, (H) is the variance per unit length of the tube but a more useful parameter to the analyst is the volume variance (s_v²). This can be derived using the relationship predicted by the Plate Theory (see book 6).

              where (Vo) is the volume of the tube

                     and (l) is the length of the tube

Now , consequently

Thus, expression for the volume standard deviation () for tubes of different length is

                                                                 (1)

Employing equation (1) it is possible to calculate the value of () for a range of cylindrical connecting tubes of different radii and different lengths.