Scale used to evaluate interference competition

[JASON K. DOBRANIC]

	I was wondering if any of you working on interference competition 
bioassays have a good scale for evaluating reaction types. I am so far 
aware of the following one using the index of antagonism:


Points				Reaction type 

A		Mutual intermingling of the two organisms
0

B		Mutual inhibition on contact; the space between the colonies 
1		is small but clearly marked

C		Mutual inhibition at a distance
2

D		Inhibition of one organism on contact; the antagonist 
3		continues to grow, unchanged or at a reduced rate, through 
		the colony of the inhibited organism.

E		Inhibition of one organism at a distance; the antagonist 
4		continues to grow through the resulting clear zone at an 
		unchanged or reduced rate.

Index of Antagonism:

IA = [n(A*0) + n(B*1) + n(C*2) + n(D*3) + n(E*4)] / the number of trials

where n is the frequency of the reaction type.
(After Wicklow et al, 1980; Strongman, 1986)

Is there in your opinion a better way of evaluating this? Also for slow 
growing antagonists it seems difficult to choose between C and E.
Thanks for any help!