Stats Ch 1-Ch 3

Individuals

Objects described by a set of data. Usually people, could be animals or things

Variable

Characteristic of an individual. Can take different values for different individuals.

Data

Actual measuremnts records for individuals.

Categorial Variable

Places an individual into one of several groups or categories. Ex: eye color & occupation

Numerical Variable

When arithmetic operations such as adding and averaging make sense. Also referred to as a quantitative variable. Ex: age & income

Response variable

Measures outcome or result of study

Observational study

Observes individuals and measures variables of interest but does not intervene in order to influence the responses.

Sample survey

Survey of group of individuals by studying only some of its members, they represent a larger group.

Population

Entire group of individuals we want information about

Sample

Part of the population from which we actually collect information and is used to draw conclusions.

Census

Sample survey that attempts to include the entire population in the sample.

Experiment

Deliberately imposes some treatment on individuals in order to observe their responses. The purpose is to study whether the treatment causes a change in the response.

Statistic

Based on sample data

Parameter

Based on population data

Bias

Systematically favors certain outcomes

Convenience sampling

Selection of whichever individuals are easiest to reach (interviewer makes the choice of who to sample) -Biased

Voluntary response sample

Individuals choose themselves by responding to a general appeal. (people choose whether to response) -Biased

Simple Random Sample (SRS)

Consists of individuals from the population, chosen in such a way that every set of individuals has an equal chance to be the sample actually selected.

Under coverage

Groups in the population that are left out of the process of choosing the sample -Bias

Nonresponse

Individual chosen for the sample can’t be contacted or refuses to participate. -Bias

Response bias

A systematic pattern of incorrect responses in a sample survey. (most often linked to the wording of questions)