Population

group of individuals of the same species that live in the same area

population parameter

A characteristic or measure of a population.

raw data

The original data as it was collected from a sample.

Sample

a subset of the population

sample statistic

a numerical measure that describes an aspect of a sample

margin of error

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Confidence Interval (CI)

Given a sample from a population, the CI indicates a range in which the population mean is believed to be found. Usually expressed as a 95% CI, indicating the lower and upper boundaries. (sample statistic -+margin of error)

biased sample

a sample that is not representative of the population

random sample

a sample in which every element in the population has an equal chance of being selected

simple random sampling

a probability sampling procedure in which every sampling unit has a known and equal chance of being selected

Census

A complete enumeration of a population.

representative sample

a sample that accurately reflects the characteristics of the population as a whole

systematic sampling

Every nth item in the target population is selected

convenience sample

a form of nonprobability sample using respondents who are convenient or readily accessible to the researcher�for example, employees, friends, or relatives

cluster sampling

An economically efficient sampling technique in which the primary sampling unit is not the individual element in the population but a large cluster of elements, clusters are selected randomly

stratified sampling

A type of probability sampling in which the population is divided into groups with a common attribute and a random sample is chosen within each group

observational study

research that gathers data in a real-world setting without intentionally manipulating any variable

experimental research

gathering primary data by selecting matched groups of subjects, giving them different treatments, controlling related factors, and checking for differences in group responses

subjects/participants

people on whom we experiment

variables of interest

the items or quantities that the study seeks to measure

explanatory variable

a variable that we think explains or causes changes in the response variable

response variable

a variable that measures an outcome or result of a study

retrospective study(case-control)

an observational study in which subjects are selected and then their previous conditions or behaviors are determined

prospective study(longitudinal study)

an observational study in which subjects are followed to observe future outcomes

treatment group

the group that receives the treatment

control group

In an experiment, the group that is not exposed to the treatment; contrasts with the experimental group and serves as a comparison for evaluating the effect of the treatment.

Confounding bias

Occurs when factor is related to both exposure and outcome, but is not the the causal pathway; factor distorts or confuses effect of the exposure on outcome

confounding variable

a factor other than the independent variable that might produce an effect in an experiment

placebo effect

the phenomenon in which the expectations of the participants in a study can influence their behavior

Placebo

something which has a positive mental effect, but no physical effect

experimenter effect

a threat to internal validity in which the experimenter, consciously or unconsciously, affects the results of the study

single-blind study

study in which the subjects do not know if they are in the experimental or the control group

double-blind study

An experiment in which neither the participant nor the researcher knows whether the participant has received the treatment or the placebo

Blinding

any individual associated with an experiment who is not aware of how subjects have been allocated to treatment groups

meta-analytic study

Combined results from numerous studies to assess the effect of common variables

peer review

A process by which the procedures and results of an experiment are evaluated by other scientists who are in the same field or who are conducting similar research.

selection bias

A polling error in which the sample is not representative of the population being studied, so that some opinions are over- or underrepresented

participation bias

occurs any time participation in a study is voluntary

self-selected survey

is one in which the respondents themselves decide whether to be included

Statistics

Collection of methods for planning experiments, obtaining data, organizing, summarizing, presenting, analyzing, interpreting, and drawing conclusions based on data.