AP Statistics Unit 4

Stratified Random Sample

splits population into groups (strata) and chooses a simple random sample from each strata

Low Bias & Low Variability

good estimates

Cluster Sample

sample all from some groups

Systematic Random Sample

choose a random starting point, use intervals

Undercoverage

when some members of a population cannot are less likely to be included in a sample

Response Bias

pattern of inaccurate results

Nonresponse

when an individual is part of a sample but chooses not to respond

Obersevational Study

no treatment

Experiment

treatments imposed, allows us to show causation

Experimental Unit

what/who treatment is imposed on

Treatments

what is done or not done to experimental units

Control Group

used to provide baseline data for comparison

Blinding

when subjects and/or experimentor who interact are unaware of what treatment is given

Placebo Effect

when a fake treatment is used

Block

group of experimental subjects that are similar

Randomized Block

seperate subjects into blocks and then randomly assign treatments within each block

Matched Pair Design

subjects are paired and then randomly assigned to a treatment, each subject receives 2 treatments

Statistically Significant

when results from a study are too unusual to have occured purely by chance