Sample Size
 a part of population that is representative of the population
 ex. when you have to use data that is just way too broad
 the goal is to get enough information from a small group within a population to make predictions or conclusions about the whole population
N = population size e = margin of error (percentage in decimal form) z = zscore
zscore
is the number of standard deviations a given proportion is away from the mean
Random Sample
 a way of selecting a sample from a population so that every possible type of the sample has an equal chance of being chosen
 this will reduce the sampling bias
Statistical Power
 the probability of getting meaningful results from a test
Hypothesis Testing
 a way to see if a survey or experiment has meaningful results
Margin of Error

maximum amount that the sample reuslts are expected to differ from those of the actual population

to calculate the margin of error you need:
 population size
 sample size
 confidence level

when executing A/B test, it is important to know about margin error
 if a returns 5% and b returns 3%, yet the margin of error is 2%, a overlaps the result of the b, therefore, the result is not statistically significant