How do I figure this out using the probability density function? How do I figure this out? Well, I say the probability of taking 2 left steps, that's how I calculated it. If you actually click on the cell, you'll see that, is equal to 1 over the standard deviation, 1.581. And I just directly referenced the cell there. Divide it times the square root of 2 pi. And I always go on in awe of the whole notion of e to the i pi is equal to negative 1 and all of that.