Unit 3: Sampling & Experimental Design

This set of vocabulary flashcards covers the fundamental concepts of sampling methods, potential biases, and experimental design principles based on the Unit 3 lecture notes.

Sampling

The process of collecting data from a sample to draw conclusions about a population.

Voluntary Response Sample

A sample consisting of people who choose to include themselves by responding to a question or survey, often representing the opinions of those who feel strongly about a subject.

Convenience Sample

A type of sample that chooses individuals who are easiest to reach, which often results in biased or useless data.

Bias

A characteristic of a study design that systematically favours certain outcomes over others.

Random process

A process that has two or more possible outcomes with a known probability of being observed.

Simple Random Sample (SRS)

A sample of size $n$ consisting of individuals from the population chosen in such a way that every group of $n$ individuals has an equal chance to be the sample actually selected.

Stratum

A group of individuals within a population who are similar in ways expected to affect their response.

Stratified Random Sampling

A sampling method where the population is divided into strata, and an SRS is taken within each of those strata.

Multistage Sampling

A sampling method used for large-scale surveys where an SRS is taken at successive levels, such as selecting cities, then neighborhoods, then blocks.

Systematic Random Sample

A sampling procedure where individuals are selected from a numbered list starting with a randomly selected number from $1$ to $k$, and then every $k$th individual after that.

Sampling Interval ($k$)

The value calculated as $k = \frac{N}{n}$, where $N$ is the population size and $n$ is the sample size, used to determine the step size in systematic random sampling.

Census

A sample of the entire population.

Leading Question

A question worded in a way that suggests a particular answer or influences respondents to favor one outcome over another.

Nonresponse

A problem in sampling that occurs when selected respondents refuse to answer the survey questions.

Undercoverage

A sampling problem that occurs when some units in the population have no chance of being included in the sample.

Observational Study

A study that measures values of variables on an individual without attempting to influence or change the responses.

Experiment

A study that deliberately imposes some treatment on individuals in order to observe their response to the treatment.

Confounding

A situation where the effects of two variables (explanatory or lurking) on a response cannot be separated.

Experimental Units

The individuals on which an experiment is performed.

Subjects

Experimental units that are human beings.

Treatment

A specific set of experimental conditions applied to units; the combination of factor levels applied to a unit.

Factors

The explanatory variables in an experiment.

Factor Levels

The different values or categories assigned to the explanatory variables (factors) in an experiment.

Interaction

The condition where the effects of several factors on the response variable are examined simultaneously to see how they impact one another.

Completely Randomized Design (CRD)

An experimental design in which all experimental units are randomly assigned to receive the various treatments.

Placebo

A dummy treatment that is known to have no physical effect, used to account for psychological responses.

Placebo Effect

When a subject responds to a treatment or perceives a benefit because they believe the treatment should be helpful, rather than due to its physical properties.

Control Group

A group used for comparison in an experiment that receives a placebo, no treatment, or a standard known treatment.

Double-Blind Experiment

An experiment in which neither the subject nor the person administering the treatment knows which treatment is being applied to eliminate bias.

Replication

The administration of each treatment to more than one unit to reduce variation in the results and make them more trustworthy.

Block

A group of experimental units or subjects that are similar in ways that are expected to affect the response to treatments.

Randomized Block Design (RBD)

An experimental design where the random assignment of treatments to units is carried out separately within each established block.