Within the kinetic theory of an ideal gas, the flux of particles having a n
umber density n, and average velocity (v) over bar impinging on a plane fro
m one side, is sometimes written in textbooks as n (v) over bar /6 and some
times as n (v) over bar /4. The validity of each expression is worked out h
ere with emphasis on their effect on the pre-factor for the expressions of
the transport parameters such as viscosity, diffusion coefficient and heat
conductivity. It is shown that n (v) over bar /4 is valid in equilibrium wh
ile only when there are gradients, effectively the flux becomes n (v) over
bar /6. For the correct derivation of the transport parameters the introduc
tion of a distribution function for the collision times or mean free paths
is essential. A methodology is suggested on how to teach this subject to un
dergraduate and graduate students.