Sampling

Population - entire group of individuals, ex . all of Cypress

Sample - those being studied group must be representative of population

Sampling Frame - individuals in the population

Census - sample that includes the entire population

Sampling Variability - the natural variation inherent in sampling

Parameter - a known numerical value calculated from a sample used to estimate population parameters, usually unknown

Probability Sampling Designs

Simple Random Sample (SRS) - an SRS of size n is a design where each individual has an equal chance of being selected AND each group (every possible combination of individuals) has an equal chance of being chosen

Stratified Random Sample - first subjectively divides the population into homogeneous groups called strata, then an SRS is taken from each group

Cluster Sampling - divides the population into heterogeneous groups and an SRS is taken from the clusters; some clusters are chosen and all of the elements of the cluster are used in the sample

Systematic Sample - selecting every nth individual from a population (first value is random); equal individual chance, unequal group chance

Multistage Random Sample - a sampling design which combines several methods 

Biased Sampling

Bias - systematically favoring certain outcomes

Voluntary Response - sample participants are self-selected; people with strong opinions are more likely to comprise the population, therefore results are always negatively skewed

Convenience Sampling - only collects data from a certain group of people; e.g., the first 50 people entering a basketball game

Undercoverage - a sampling design that leaves out a segment of the population

Nonresponse - the individuals selected cannot be contacted/decline due to circumstances that skew results

Response - the survey influences responses (wording effect)