Introductory Statistics: Key Concepts and Vocabulary

Vocabulary flashcards covering core introductory statistics concepts including variable types, study designs, sampling techniques, and sources of statistical bias.

Categorical variable

A variable that takes on values representing physical attributes, categories, or labels (such as gender, hair color, ZIP code, or genre) for which numeric calculations like averages do not make sense.

Quantitative variable

A variable that deals with numerical measurements or counts where arithmetic operations (such as finding an average height, duration, or box office revenue) are meaningful.

Population

The entire group of individuals about which a researcher or statistical study wants to gather information.

Census

A study that attempts to collect data from every single individual within an entire population.

Sample

A subset of individuals selected from a population, used to collect data and estimate population values.

Observational study

A study that measures variables of interest without attempting to influence or affect responses, which cannot establish cause-and-effect relationships.

Experiment

A study that deliberately imposes treatments on individuals to elicit a response, allowing researchers to establish cause-and-effect relationships.

Individual

A single entity or object described in a dataset, such as a person, car buyer, artifact, movie, or tree.

Sample size

The specific number of individuals selected from a population to participate in a study.

Bias

A systematic flaw in the design of a statistical study that makes it very likely to consistently underestimate or overestimate the true population value.

Volunteer sampling

A sampling method where individuals voluntarily choose themselves to participate in a study, often leading to strong opinion bias.

Convenience sample

A non-random sampling method that selects individuals who are easiest to reach or happen to be at a specific place and time, which typically fails to represent the population.

Random sample

A sample collected using a chance mechanism to ensure every individual in the population has a known chance of selection, minimizing bias.

Undercoverage

A type of bias that occurs when some groups or members of the target population are completely left out of the sampling process.

Nonresponse

A type of bias that occurs when a chosen individual for a sample cannot be contacted or refuses to participate in the study.

Response bias

A type of bias occurring when there is a consistent pattern of inaccurate, untruthful, or influenced responses in a study.

Selection bias

A bias caused by researchers choosing to include or exclude specific individuals from a sample, which random sampling eliminates.

Simple random sampling

A sampling technique conducted without replacement where every sample of a given size $n$ has an equal chance of being selected.

Sampling variability

The natural occurrence where different random samples of the same size drawn from the same population yield different sample estimates.