Gabbagabito

Hello, I'm starting PhD this Fall in the US, and have been asked whether I would like to fill out a W-8BEN form. I understand this form has to do with claiming a tax treaty and something to do with getting a lower amount of money withheld. I also know Canada and US have some sort of a tax treaty. But I'm pretty unsure as to whether I should fill this out—and step 2, how I should fill out section II if I am supposed to fill it out. Have other Canadians studying in US run into this? Have you filled out the form? I will have stipend income greater than 10,000 from the school. Any help greatly appreciated!