This is personal study note Copyright and original reference: https://www.youtube.com/watch?v=fx4tCRiynMQ&list=PLsri7w6p16vtEz_J1G7HQG-Rm8vpZPtPS&index=3 ================================================================================ Test on hypothesis (about estimated population mean) - when you don't know population's variance ================================================================================ If number of sample $$$n \to \infty $$$, "sample std" becomes "population std" regardless of population's normality - use z statistics ================================================================================ When you have small number of sample use t-statistics use "sample std" ================================================================================ Relation between t and z z: special case (when you have enough number of sample) ================================================================================ Example statistic t