Std vs variance - std is in the same metric as the mean, is the root of variance., allows outliers to influence, will not result in samples cancelling each other without the square root in the formula.
what are the known facts? Inherent in both probability and statistics is a population,
every individual we are interested in studying, and a sample, consisting of the individuals that are selected from the population.
in probability: would start with us knowing everything about the composition of a population, and then would ask, “What is the likelihood that a selection, or sample, from the population, has certain characteristics?”
In statistics: we have no knowledge about the types of socks in the drawer. we infer properties about the population on the basis of a random sample.