I took my MSF course last week.  The second day,   I began to struggle with accidentally rolling on the throttle when practicing the quick stop.  Is this a common problem for beginners, or does it happen more with people who have little hands?  I guess I'm wanting to know, "Is it just me?"  Whether it's related to my hand size, or my motor skills, I've got to learn to overcome it before I do anything else (for my sake and everyone else's).  Any tips?  

I don't want to say it should not happen just because it never happened to me. Different people have different "problems" in the beginning simply because there is so much to pay attention to (traffic, controls, balancing the bike, etc.)

I think that the problem might be in your right hand's position. Are you squeezing the front brake and rolling down the throttle at the same time?

What should help, is squeezing the clutch at the same time as the front brake (you should be doing this during quick stops anyway). Then, even if you roll the throttle, it won't do any harm (besides making noise), since the gears will not be engaged.  

Clutch is in... I think what is happening is that I have to move my whole hand to reach the brake effectively due to short fingers... then as I shift my hand back to it's normal position on the throttle, I end up rolling it a bit.  Does that make sense?  

This happened to me a few times while I was learning, so its not just you.  I just overcame it with practice.  If your hands are small perhaps your brake lever can be adjusted to work better for you.  Talk to your mechanic.  

Check your hand position when you start. Odds are you are starting with your wrist in positive flexion (bent towards the front of the wrist). So, when you grab for the brake, you end up with throttle.

Let me know if I;m right or wrong. I want to do the MSF instructor course, and I don't want to give out any advice that's wrong.

Thanks  

I really think that I am starting with my wrist low, but my fingers literally just graze the lever, rather than being able to reach around to squeeze it, so to get the extra length, up pops the wrist.  

Keeping a low wrist will fix the problem. I would check and see if there are any ways to adjust the brake lever so you don't have to bring your wrist up to engage the brake.