Modify: use math font of expected value
Modify: change equation
Modify: change equation
Modify: change equation with {\rm hoge}
Modify: change equation
Modify: St to {\rm St}
Modify: N to {\rm N} : Gaussian distribution
Modify: var to {\rm var}
Modify: X to \bm{X}
Modify: compress sentence
Modify: x, m -> use bm{}
Modify: use \bm
Modify: untabify
Modify: fix small typo
Modify: \bm{x} to x
Remove: the frame where I explaned
Modify: x to vector
Modify: align equation
Modify: tag version 2.0
Modify: add explanation of sufficient statistic