confidence intervals:
if want to use normal distribution, has to check N*p > 5 and N(1-p) > 5
margin of error=z*SE=z*sqrt(p(1-p)/n), z=1.96 if alpha=5%
confidence interval: [p-MOE, p+MOE]
Hypothesis test
alpha=P(rejected null | null is true) 错判
beta=P(fail to reject null | null is false) 漏网之鱼
power=1-beta
