Don,

I have carefully read your protocol for DBT of cables, and it seems to me
airtight. You've covered all the places where most tests fail, and I would
add only a couple of things:

Don't let the subject know how he's doing until the test is over. Also,
make sure you remove the cables before you flip the coin, so that the time
required to make the change will be constant even when no change is called
for.

You might consider 18 trials, since 13 out of 18 comes closer to the 5%
dividing line between success and failure.

Norm Strong