Population A collection of all individuals of a circumscribed type, or a generative process from which we can generate samples.
Sample A subset of a population – individuals we measure.

Parameter A true measure of a population.
Estimate A guess at a parameter that is made from a finite sample.

Sampling error describes the deviation between parameter and estimate attributable to the finite process of sampling.
Sampling bias describes the deviation between parameter and estimate attributable to non representative sampling.
Independence Samples are independent if the probability that one individual is studied is unrelated to the probability that any other individual is studied.

Explanatory variables are variables we think underlie or are associated with the biological process of interest.
Response variables are the outcome we aim to understand.