Then it's standard z-score is 3 and 1 half. But anyway, let's focus on the purpose of this video. So that's what the normal distribution, I guess the probability density function for the normal distribution looks like. But how did it get there? I guess even more importantly, by the end of this video you should at least feel comfortable that this is a good approximation for the binomial distribution if you take enough trials. And that's what's fascinating about the normal distribution is that if you have the sum, and I'll do a whole other video on the central limit theorem, but if you have the sum of many, many independent trials approaching infinity, that the distribution of those, even though the distribution of each of those trials might have been non-normal, but the distribution of the sum of all of those trials approaches the normal distribution. And I'll talk more about that later.