29th May Learning summary of probability

Today we learned about how to calculate permutations of groups more precisely,

like N=4, so there are 4 groups, and each group of them have 6 (3 x 2)permutations, which is 4 x 6 = 24 

if N= 5, then there 5 groups, each group have 24 ( 4 x 3 x 2), which is 5 x 24 = 120

Or the other way to think of it is, we assign 4 people to the seats, then the first one could 4 possibilities to choose, and second one could have 3 possibilities to choose ( because the first one has already taken one of four seats already), then the third only have 2 choices to make, which let the last one have nothing but only the left to choose.

So is 4 x 3 x 2 x 1 = 24

Okay, though my brain is still a lit bit twisted right now, I think I got clear ideas of how permutations-calculating operates, awesome!!! 

Variance is the measure of on an average to see how far each point is from the average, then we can have clearer idea how data is distributed.

Then the average of annual salary in Taiwan is far beyond the truth of reality won't happen XD