-**Random sample** - every element of population has equal chance of selection
-**Population proportion $p$** - proportion of individuals in population with an attribute
-**Sample proportion $\^p$** -
+**Random sample** - every element of population has equal chance of selection (exactly representative)
+**Population mean $\mu$** - mean of all values of one attribute in population. $\mu = {\Sigma \text{values} \over |\text{population}|}$
+**Sample mean $\overline{x}$** - mean of all values in a sample. Random variable.
+**Population proportion $p$** - proportion of defectives in population (100% certainty)
+**Sample proportion $\hat{p}$** - proportion of defectives in one sample (varies between samples)