Taammi P.

Variable

A characteristic of the individual being measured or observed.

Population Parameter

A *numerical* measure that describes an aspect of a population.

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sample statistic

A *numerical *measure that describes an aspect of a sample.

Nominal (name) level

Data that consist of names, labels, or categories.

Rank order for ordinal level variables.

Height can be ranked by students standing tallest to shortest, but we don't know the difference in height between each student.

Interval variable

- The difference between values can be measured.
- The difference between a temperature of 100 degrees and 90 degrees is the same difference as between 90 degrees and 80 degrees.

Ratio Variable

- A
*ratio*variable, has all the properties of an interval variable, and also has a clear definition of 0.0 - Zero equals nothing or none

Sampling Frame

Population from which the sample is drawn.

Undercoverage

results from omitting population members from the sample

frame.

frame.

sampling error

The difference between measurements from a sample and

corresponding measurements from the respective population.

corresponding measurements from the respective population.

nonsampling error

The result of poor sample design, sloppy data collection, faulty measuring instruments, bias in questionnaires, and so on.

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Descriptive statistics

Procedures used to summarize, organize and simplify data.

Inferential statistics

Methods of using information from a sample to draw conclusions regarding a population.

Simple Random Sample

A sample sin which every element in the population has an equal chance of being chosen.

Random Number Table

Table containing lists of numbers that are ordered on the basis of chance.

Simulation

A numerical facsimile or representation of a real-world

phenomenon.

phenomenon.

Sampling with replacement

Once a number is selected for the sample it is counted then replaced.

Stratified sampling

- Groups or classes inside a population that share a common characteristic are called strata.
- In the population of all undergraduate college students, some strata might be freshmen, sophomores, juniors, or seniors.

Systematic sampling

- Involves first selecting a fixed starting point in the larger population, and then
- Obtaining subsequent observations by using a constant interval between samples taken

Cluster sampling

- When "natural" groupings are evident in a statistical population
- The total population is divided into these groups (or clusters) a sample of the groups is selected
- Often used in marketing research

Multistage samples

A more complicated form of cluster sampling in which larger clusters are further subdivided into smaller, more targeted groupings for the purposes of surveying.

Convenience sampling

Use a sample that happens to be convenient to select

Census

Measurements or observations from the entire population.

Sample

Measurements or observations from part of the population

are used.

are used.

Simulation

A numerical facsimile of real-world phenomena

observational study-

Measures a response variable without trying to influence it.

Experiment

A treatment is deliberately imposed on one set individuals which is different than the treatment of another set of individuals and the differences are measured.

Placebo effect

Occurs when a subject receives no treatment but (incorrectly) believes he or she is in fact receiving treatment and responds

favorably.

favorably.

Treatment group

The group that receives the prescribed treatment.

Completely randomized experiment

Where a random process is used to assign each individual to one of the treatments.

Block

A group of individuals sharing some common features that might

affect the treatment.

affect the treatment.

Randomized block experiment

- Individuals are first sorted into blocks, and
- Then a random process is used to assign each individual in the block to one of the treatments.

Control group

This group receives a dummy treatment, enabling the researchers to control for the placebo effect.

Randomization

- Used to assign individuals to the two treatment groups.
- This helps prevent bias in selecting members for each group.

Double-blind experiment

This means that neither the individuals in the study nor the observers know which subjects are receiving the treatment.

Likert scale

Scale where possible responses span from strongly disagree to strongly agree.

nonresponse

Occurs when an individual chosen for the sample can't be contacted or does not cooperate.

Hidden bias

- The question may be worded in such a way as to elicit a specific response.
- The order of questions might lead to biased responses.
- Likert scale forces responses that don't reflect respondent's feelings.

Vague wording

Words such as “often,” “seldom,” and “occasionally” which mean different things to different people.

Voluntary response

- Individuals with strong feelings about a subject are more likely than others to respond.
- Such a study is interesting but not reflective of the population.

Lurking variables

A variable for which no data have been collected but that nevertheless has influence on other variables in the study.

Confounding variable

Its a variable that has an unintentional effect on the dependent variable.

Dependent variable

The event studied and expected to change with the introduction of the independent variable.

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