Untitled Flashcards Set

census

Study that attempts to collect data from every individual in the population.

sample

Subset of individuals in the population from which we collect data.

population

In a statistical study, the entire group of individuals we want information about.

sample survey

Study that uses an organized plan to choose a sample that represents some specific population.

convenience sampling

Sample selected by taking from the population individuals that are easy to reach.

voluntary response sampling

A sample that consists of people who choose to be in the sample by responding to a general invitation.

bias

The design of a statistical study shows bias if it is very likely to underestimate or overestimate the value you want to know.

random sampling

Using a chance process to determine which members of a population are chosen for the sample.

simple random sample

Sample chosen so that every group of n individuals in the population has an equal chance to be selected.

stratified random sampling

Sample obtained by classifying the population into groups of similar individuals, called strata.

cluster sampling

Sample obtained by classifying the population into groups of individuals located near each other, called clusters.

undercoverage

Occurs when some members of the population are less likely to be chosen or cannot be chosen in a sample.

nonresponse

Occurs when an individual chosen for the sample can't be contacted or refuses to participate.

wording of questions

An important influence on the answers given in a survey that can introduce strong bias.

response bias

Occurs when there is a consistent pattern of inaccurate responses to a survey question.

observational study

Study that observes individuals and measures variables of interest but does not attempt to influence the responses.

confounding

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

experiments

A study in which researchers deliberately impose treatments on individuals to measure their responses.

placebo

A treatment that has no active ingredient but is like other treatments.

treatment

Specific condition applied to individuals in an experiment.

experimental unit

The object to which a treatment is randomly assigned.

subjects

Experimental units that are human beings.

factor

Explanatory variable in an experiment.

level

Specific value of an explanatory variable in an experiment.

comparison

Experimental design principle that uses a design to compare two or more treatments.

control group

Experimental group whose purpose is to provide a baseline for comparing the effects of treatments.

placebo effect

Describes the fact that some subjects respond favorably to any treatment, even an inactive one.

double-blind

An experiment in which neither the subjects nor those measuring the response know which treatment was received.

single-blind

An experiment in which either subjects or those measuring the response know which treatment was received.

random assignment

Experimental design principle that uses chance to assign experimental units to treatments.

control

Experimental design principle that mandates keeping other variables the same for all experimental units.

replication

Experimental design principle that involves repeating an experiment under the same conditions.

completely randomized design

Design in which the experimental units are assigned to treatments completely by chance.

block

Group of experimental units known to be similar in some way that affects the response to treatments.

randomized block design

Experimental design that begins by forming blocks of individuals that are similar in some way.

matched pairs design

Common form of blocking for comparing just two treatments.

sampling variability

The fact that different random samples of the same size produce different estimates.

inference

Drawing conclusions that go beyond the data at hand.

margin of error

The difference between the point estimate and the true parameter value in C% of all samples.

statistically significant

When the observed results of a study are too unusual to be explained by chance alone.

anonymity

The names of individuals participating in a study are not known even to the director of the study.

confidential

A principle of data ethics requiring that an individual's data be kept private.

informed consent

Principle that individuals must be informed in advance about the nature of a study.

institutional review board

Board charged with protecting the safety and well-being of participants in a planned study.

inference about cause and effect

Conclusion from experiment results that treatments caused the difference in responses.

inference about a population

Conclusion about the larger population based on sample data.