simple random sample
individuals from a population are chosen so that each individual has an equal chance of being selected
systematic sample
members from a larger population are selected according to a random starting point but with a fixed, periodic interval
stratified random sample
members of the population are grouped then members from each group are randomly selected
cluster sample
members of the population are grouped then a set number of groups are randomly selected
bias
refers to the tendency of a process that tends to over- or under-estimate the value of a population parameter
convenience sampling
choosing individuals that are easiest to reach
voluntary response sampling
individuals choose themselves by responding to a survey or willingly participating in an experiment
undercoverage
occurs when some part of the population is not sampled at all or at a smaller proportion than seen in the population
nonresponse bias
occurs when some subjects won’t respond or participate
response bias
subjects may lie or mislead, intentionally or unintentionally
control
efforts made to minimize lurking variables
replication
the use of enough subjects to reduce chance variation
experiment
a treatment is deliberately imposed on individuals in order to observe their responses
observational study
individuals are observed and variables of interest are measured without any attempt to influence responses
treatment
a specific experimental condition applied to the subjects of an experiment
parameter
a numerical characteristic of a population
population
the entire pool from which a statistical sample is drawn
statistic
a numerical characteristic of a sample
sample
a small part or quantity intended to show what the whole is like
census
a sample that consists of the entire population