Statistics Vocab

Bias

A question that is flawed in a way that leads to inaccurate results.

Biased question

A question that is flawed in a way that leads to inaccurate results, such as "Do you agree that we should take a field trip to a science museum this year?" because it encourages a particular response.

Biased sample

An error that results in a misrepresentation of a population, such as when an environmental magazine sends out a survey on recycling to its readers who likely have a strong opinion about recycling, thus overrepresenting that viewpoint.

Cluster sample

A sample in which a population is divided into groups (clusters), and all members in one or more clusters are randomly selected.

Confidence interval

An interval that has c% probability of containing the actual value of a population parameter, typically represented as (x - E, x + E), where E is the margin of error.

Control group

The group in an experiment that is subjected to no treatment under ordinary conditions to serve as a baseline for comparison.

Controlled experiment

An experiment in which two groups are studied under identical conditions except for one variable, typically with a treatment group and a control group.

Convenience sample

A sample in which only members of a population that are easy to reach are selected.

Descriptive statistics

The branch of statistics that involves organizing, summarizing, and displaying data to describe its main features.

Experiment

A method that imposes a treatment on individuals to collect data on their response to the treatment in order to test hypotheses.

Hypothesis

A claim or statement about a characteristic of a population that is subject to investigation and testing.

Inferential statistics

The branch of statistics that involves using sample data to make inferences or predictions about a population.

Information design

The process of designing data and information so that it can be easily understood and used effectively.

Margin of error

The maximum expected difference between a sample result and the population parameter it estimates, often represented as a percentage.

Normal curve

A type of probability distribution that is symmetric and bell-shaped, representing the distribution of many naturally occurring phenomena.

Normal distribution

A continuous probability distribution characterized by a symmetric, bell-shaped curve.

Observational study

A study in which individuals are observed and variables are measured without intervention or manipulation by the researcher.

Parameter

A numerical summary of a population characteristic.

Placebo

A harmless substance or treatment with no therapeutic effect, often used in controlled experiments to test the efficacy of another treatment.

Probability distribution

A function that assigns probabilities to the outcomes of a random experiment.

Population

The entire group of individuals or instances about which we want information.

Random sample

A sample in which each member of the population has an equal chance of being selected.

Random variable

A variable whose value is subject to variations due to chance.

Randomization

The process of randomly assigning subjects to different treatment groups or experimental conditions.

Randomized comparative experiment

An experiment in which subjects are randomly assigned to either a control group or a treatment group to compare the effects of different treatments.

Replication

The repetition of an experiment or study under similar conditions to validate or refute the results.

Sample

A subset of individuals or instances from a larger population.

Sampling distribution

The probability distribution of a sample statistic based on all possible samples of a given size from a population.

Self-selected sample

A sample in which individuals voluntarily choose to participate, potentially introducing bias.

Simulation

The use of a model or computer program to mimic a real-world process or situation.

Standard error of the mean

The standard deviation of the sampling distribution of the sample mean.

Standard normal distribution

A normal distribution with a mean of 0 and a standard deviation of 1.

Statistic

A numerical summary of a sample characteristic.

Stratified sample

A sample obtained by dividing the population into homogeneous subgroups and then randomly selecting samples from each subgroup.

Survey

A research method that collects data from a sample of individuals or instances to generalize findings to a larger population.

Systematic sample

A sample obtained by selecting every nth individual from the population after an initial random start.

Treatment group

The group in an experiment that receives the treatment or intervention being studied.

Unbiased sample

A sample that is representative of the population and is free from systematic error or bias.

Z-score

A standardized score that indicates how many standard deviations a data point is from the mean in a normal distribution.

Standard deviation

A measure of the amount of variation or dispersion of a set of values.