stat 2300 1.4-.6

stratified sample

guarantees that each stratum is represented in the sample. divides the population into separate groups called Strata and then selects are simple random sample from each stratum. The individuals within its stratum should be homogeneous or similar in someway with respect to the variable of interest.

strata

definite subgroups in a population

cluster sample

*selects whole cluster* divides the population into a large number of clusters such as city blocks. Then a simple random cluster is selected and all individuals in the selected clusters are included for the sample. For personal interviews when the subjects of a cluster or close geographically cluster sampling is less expensive per observation then simple random sampling.

systematic sampling

obtained by selecting every KTH individual from a population. The first individual selected corresponds to a random number between one and K. Systematic sampling does not require a list of individuals in the population.

clusters

small groups of people or things that are close together

convenience sample

choosing individuals who are easiest to reach, suspect data, uses voluntary response samples

voluntary response samples

People decide whether to join a sample based on an open invitation; particularly prone to large bias.

Bias

leads to a sample that is systematically different from the population with respect to the variable of interest

sampling bias

a flawed sampling process that produces an unrepresentative sample (non-random sampling, under coverage)

No response bias

bias that results when respondents differ in meaningful ways from non-respondents

response bias

tendency of subjects to systematically respond to a stimulus in a particular way due to nonsensory factors, maybe they are lying or wording of questions or misleading or confusing questions

experiment

A controlled study conducted to determine the effect that is very in one or more explanatory variables or factors has on a response variable. has causation

factors/explanatory variables

causes response variable

treatment

any combination of the values of the factors

experimental units

the persons or objects upon which a treatment is applied

subjects

Experimental units that are human beings.

control/comparison group

allows the researcher to analyze the effectiveness of the primary treatment. serves as baseline

placebo

A harmless pill, medicine, or procedure prescribed more for the psychological benefit to the patient than for any physiological effect. ppl think that they get something. usually control group won't get anything.

Randomization

a process of randomly assigning subjects to different treatment groups

blinding the study

allows the researcher to treat the treatment groups as equally as possible, single-blind and double blind

single-blind experiment

an experiment in which the participants are unaware of which participants received the treatment

double-blind experiment

an experiment in which neither the experimenter nor the participants know which participants received which treatment

replication

repeating the essence of a research study, usually with different participants in different situations, to see whether the basic finding extends to other participants and circumstances

design

to describe the overall plan in conducting the experiment

completely randomized design

each experimental unit is randomly assigned to a treatment