Research Methods Sampling

Population

the entire set of people or products in which you are interested

Sample

a smaller set, taken from that population

Biased Sample

some members of the population of interest have a much higher probability than other members of being included in the sample (unrepresentative sample)

Unbiased Sample

all numbers of the population have an equal chance of being included in the sample (representative sample)

Convienience Sampling

using a sample of people who are easy to contact and readily available to participate

Self-Selection

a term used when a sample is known to contain only people who volunteer to participate

Probability Sampling (random sampling)

every member of the population of interest has on equal and known chance of being selected for the sample

Simple Random Sampling

assigning numbers to individuals in a population and selecting certain ones based on random numbers

Systemattic Sampling

using a computer or random number table the research selects two random numbers and counts off

Non-probability Sampling

techniques involve nonrandom sampling methods where not all members have a chance of being selected.

Cluster Sampling

an option when people are already divided into arbitrary groups (random)

Multistage Sampling

two random samples are selected, a random sample of clusters and then a random sample of people within those clusters

Stratified Random Sampling

the researcher purposefully selects particular demographic categories, or strata, and then randomly selects individuals within each of the categories, proportion to their assumed membership in the population

Weighting

adjust data so response from members that are underrepresented in categories count more and overrepresented members count less

Oversampling

the researcher intentionally overrepresents one or more groups

Random Assignment

when researchers want to place participants into two different groups, usually assign them at random

Purposive Sampling

researchers want to study only certain kinds of people, they recruit only those particular participants

Snowball Sampling

helps researchers find rare individuals

Quota Sampling

researcher identifies subsets of the population of interest and then sets a target number for each category in the sample

Census

Testing everyone in the population

Margins of Error

a tolerable degree of deviation from a correct or exact value or target ( + or - 3%) - larger the sample size, smaller this is