[Wookai]

I haven't done it yet, but I could. This also depends on what your goal is, and how long the campaign last, but it is quite easy to extract such probabilities of success. For instance, this plot shows the estimated probability of success as a function of time and the proportion of the goal that was pledged: http://imgur.com/hoTzBEW. From it, you can see that you need to be at about 25% or more of your goal in the middle for your campaign if you want to have more chances of success than failure. Similar plots could be done by including more factors.