stats chapter 4

strata / stratified random sample

Strata: group of similar individuals

Stratified random sample: classify the population into strata, then choose a separate SRS in each stratum and combine these SRS to form the full sample

cluster / cluster sample

Cluster: groups that mirror the variety of the whole pop.

Cluster sample: divide pop. into clusters, then choose an SRS of the clusters, all individuals in the chosen cluster are included in the sample

undercoverage

occurs when some groups in the pop. are left out of the process of choosing the sample

nonresponse

occurs when an individual chosen for the sample can’t be contacted or refuses to participate

lurking variable

a variable that is not among the explanatory or response variable in a study but that may influence the response variable

confounding variable

occurs when two variables are associated in such a way that their effects on a response variable can’t be distinguished from each other

block / randomized block design / matched pair design

block: group of experimental units that are known before the experiment to be similar in some way that is expected to affect the response to the treatments

randomized block design: random assignment of experimental units to treatments is carried out separately within each block

matched pairs design: type of randomized block design for comparing two treatments; create blocks by matching pairs of similar experimental units