Population: the entire collection of units about which we would like information. ( e.g. all of the 1 bedroom apartments in State College).

Sample: the collection of units we actually measure ( e.g. 15 of the 1 bedroom apartments in State College).

Parameter: the true value we hope to obtain ( e.g. true average cost of 1 bedroom apartment in State College).

Statistic: an estimate of the parameter based on observed information in the sample ( e.g. average price of 15 sampled 1 bedroom apartments).