Hey man, your channel is probably the best if not one of the best channels on youtube. You should write a book on first to last data science concepts with code and explanations! The way you teach things in such a simple manner is absolutely amazing. I understand all the hard concepts thanks to your intuitive explanation. Thanks!
the way you present all these explanation is so easy and clear to understand, which could have been hundred times fuzzier had it been done from "usual professor".
In physics there is the rule of thumb, that a difference in mean values is probably significant if that difference is larger than three standard deviations (3 \sigma) of the distribution. As the standard deviation shrinks with the square-root of the sample-size (the central limit theorem), one can easily estimate the number of required samples. From this one also gets an intuition why we need more samples to have a lower standard-deviation to significantly confirm a smaller difference in the mean of both distributions.