Here is another link:

http://www.familysearch.org/Eng/Search/RG/guide/WLSpanis19.asp#racial_te
rminology

So......according to the link above:
Coyote = Spanish (1/2), Indian (3/8), and Negro (1/8)

I doubt the science was ever that accurate.  As someone mentioned 
earlier, I imagine, it had more to do with your complexion and your 
parents complexion.  Besides someone who is a farmer is going to get 
more sun then someone who owns a hacienda.  They might have the same 
amount of Spanish and Indian blood but one is going to be classified as 
Espanol and the other will be classified as Mestizo.  Plus who could 
keep up when someone who was Coyote married someone who was mestizo or 
lobo, etc...

Just my two cents...
Angie