We think we have four sets of people:

Detroiters who distinguish.
Class members who distinguish.
Detroiters who do not distinguish.
Class members who do not distinguish.

1. How do we define distinguisher for Detroit group?

Then ...

For each of these sets of people, we want to know ...
2. Is there a significant difference between F1 values for 
<hawed> and F1 values for <hod>?
What about for F2 values?
What about for duration values?
3. If we normalize for the vocal tract length differences among
the talkers in each group, are there "predictive" differences?

Also, for each larger group (Detroiters versus class members), 
is the difference in correct identification and in formant values 
bimodal (as we'd expect if there were two clearly distinct groups),
or is it continuous?

If there are continua, what is the relationship between the 
production continuum and the perception continuum?