https://en.wikipedia.org/wiki/Central_limit_theorem
For example, even 300 really random people is enough to correctly assertain the distribution of population for some measurement (say, some personality feauture).
That’s the basis of all polls and what have you
I think you might be thrashing around 30 samples for a normal distribution and the Central Limit Theorem and accidentally added a zero!
(OK, on rereading, you did link to a WP article about CLT, so 30 it is!)