What allows us to apply normal calculations to non-normal distributions?

Explanation:

Many data sets naturally fit a non normal model. For example, the number of accidents tends to fit a Poisson distribution and lifetimes of products usually fit a Weibull distribution. However, there may be times when your data is supposed to fit a normal distribution, but doesn’t. If this is a case, it’s time to take a close look at your data

accelerated heartbeat, raise in blood pressure, slow in digestion, raise in blood sugar and perspiration. (myers' psychology for ap 2nd edition pg 87)