Unit 3-4: Sampling, Surveys, and Experiments - Vocabulary

Vocabulary flashcards covering key terms in sampling, surveys, and experiments from the lecture notes.

Population

The entire group of individuals about which information is sought in a study.

Census

Data collected from every individual in the population.

Sample

The part of the population from which information is actually collected.

Sample survey

A study that collects data from a sample to learn about the population from which the sample was drawn.

Convenience sampling

Selecting individuals from the population who are easy to reach.

Bias

A design flaw that makes results likely to understate or overstate the value of interest.

Voluntary response sampling

People choose to be in the sample by responding to a general invitation.

Random sampling

A chance process used to determine which members of the population are included in the sample.

Simple random sample (SRS)

A sample selected so that every group of n individuals has the same probability of being chosen.

Sampling without replacement

Once an individual is selected, it cannot be selected again in the same sample.

Sampling with replacement

An individual can be selected more than once in the same sample.

Table of random digits

A long string of digits 0-9 where each entry is equally likely and independent.

Strata

Groups of individuals in a population that share characteristics related to the study variables.

Stratified random sampling

Selecting an SRS from each stratum and combining the samples into one overall sample.

Cluster

A group of individuals located near each other.

Cluster sampling

Randomly select clusters and include all members of the chosen clusters in the sample.

Systematic random sampling

Select from an ordered population by choosing one of the first k individuals at random and then selecting every kth thereafter.

Multistage sampling

A sampling plan that combines two or more sampling methods.

Sampling error

The difference between a sample estimate and the true population value due to the act of sampling.

Random sampling error

The portion of sampling error due to randomness in selecting the sample.

Undercoverage

When some members of the population are less likely to be chosen or cannot be chosen.

Sampling frame

The list from which the sample is actually drawn.

Nonresponse

When a chosen individual cannot be contacted or refuses to participate.

Response bias

A systematic pattern of inaccurate answers in a survey.

Observational study

Observes individuals and measures variables without attempting to influence responses.

Response variable

The outcome measured in a study.

Explanatory variable

May help explain or predict changes in the response variable.

Confounding

When two variables are associated in such a way that their effects on the response cannot be distinguished.

Experiment

Deliberately imposes treatments on individuals to measure their responses.

Placebo

A treatment with no active ingredient but is otherwise like other treatments.

Treatment

The specific condition applied to the individuals in an experiment.

Experimental unit

The object to which a treatment is randomly assigned.

Subject

When the experimental units are human beings.

Factor

An explanatory variable that is manipulated.

Levels

The different values of a factor.

Control group

A baseline for comparing the effects of other treatments; may receive placebo, active treatment, or no treatment.

Placebo effect

The tendency of some subjects to respond favorably to any treatment, even an inactive one.

Double-blind

Neither the subjects nor those who interact with them know which treatment is given.

Single-blind

Either the subjects or the people who interact with them don’t know which treatment is given.

Random assignment

Using a chance process to assign experimental units to treatments, balancing other variables.