Day0-notes

[sanshengshi626]

1. Population&Sample: Population mean: sum(X)/N Sample mean:sum(X)/n Population variance:sum(x(I)-mean)^2/N Sample variance:sum(x(I)-mean)^2/(n-1)(sample generally has smaller size and var is smaller, divided by n-1 make it get bigger) var=E(x^2)-E(x)^2
2. Variable: Continuous&Discrete, for continuous only interval probably is available, any specific point p is 0.
3. Binomial Distribution: C(n,k) p^k (1-p)^(n-k) E(x)=np
4. Law of large numbers: the average of the results obtained from a large number of trials should be close to the expected value, and will tend to become closer as more trials are performed.
5. Normal Distribution: {\displaystyle \varphi (x)={\frac {1}{\sqrt {2\pi }}}e^{-{\frac {1}{2}}x^{2}}} Z-score:z = (x – μ) / σ

[sanshengshi626]

day1