AP Stats Ch.11/12 Vocab

voluntary response sample

usually biased since most that volunteer have strong opinions or are more motivated than others

Convenience sampling

only accounts for those that are convenient for an outcome

Undercoverage

when certain groups of a population are not counted

Nonresponse bias

when people don’t respond to a survey

Response bias

when the wording of questions might influence a particular answer

simple random sample (SRS)

ex. assigning sample frame like #’s to a roster of people then using a random # sequence to choose a number of people.

stratified random sample

the population is split into groups (strata) and then random #’s would be assigned and randomly chosen using a random # sequence

cluster sample

population is naturally separated into clusters that resemble the population, then some of those groups are picked

Systematic sample

uses a list of individuals that are given numbers in numerical order. A random number generator generates a number that will select the start of the list. From that number, the list will continue with every nth number.

Multistage sampling

Uses a combination of different types of sampling methods. This method is used when the population is very large.

retrospective

collecting past data

prospective

collecting future data

Experimental units (subjects in people)

The individuals upon which an experiment is conducted

Controlled experiment

all treatment groups have the same environment

Randomized participants

equalize the effects of unknown or uncontrollable sources of variation

Why replicate treatments/experiments?

Itgives more consistent feedback over time

Blocking (not required)

may help separate confounding variables and lead to better results

control group

baseline untreated group/basis of comparison

single blinding

patients do not know which study group they are in

double blinding

neither the patients nor the researchers/doctors know which study group the patients are in

placebo effect

when the fake treatment yields a change in the response variable (usually mental)

randomized block design (matching)

confounding

When the levels of one factor can entangled with another factor