Calculating Steph's likely shooting percentage is kind of tricky but we can first make an estimate assuming (incorrectly) that he didn't shoot 100 3s a day, but instead stopped at 77 (if this kind of simplification bothers you then don't become a physicist). In this case his one-day probability is \({p_3}^{77}\), where \(p_3\) is his 3-point shooting percentage. Let's assume for the moment that he shoots the same percentage in practice as in an actual NBA game. Looking at his stats, in 2015 this stands at 44%. Plugging this into our equation we get:

\(p_3 = {0.44}^{77} = 3.51*10^{-28}\).

Clearly Steph shoots a bit better than that in practice. How much better? Steph has been a professional basketball player for 6 seasons. Let's say he does this shooting drill every day he practices over those 6 seasons and that adds up to a total of 1000 days. We also have to assume that this would be newsworthy, i.e. this is not something he pulls off everyday.