ap stats quiz 3.1-3.1

population

entire group we want info about

sample

part of group we actually examine, ideally represents the pop

census

when we collect datat an every individual in a pop

homogeneus

all individuals in a group (sample pop) share the same value for a particular variable (common traits)

heterogeneus

all individuals in a group do not share the same value for a particular variable

observational study

observes individuals, measures variables of interest, but makes no attempt to influence responses

experiment

when treatments are imposed on individuals in a sample, then response is measured (treatments meant to influence response)

convenience sampling

sampling individuals that are readily available (observer picks the sample)

judgment sample

when observer picks what they think is representative

voluntary response sample

individuals are allowed to join a sample if they want to (usually represents strong opinions)

simple random sample (srs)

every possible sample sze n from the population has the same probability of being selected

stratified random sample

divides pop into homogeneous groups and, within each group, takes an srs

cluster sampling

divides pop into heterogeneous groups and picks one or more of these at random to be included in the sample (every individual in the chosen groups is included)

systematic random sampling

method of sampling individuals according to random starting pt and a fixed periodic interval