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Bias
 A regular prejudice in one direction; in political polling, bias might result from polling only a certain economic
 or ethnic group, which could have unrepresentative opinions

Margin of error
 A range of numbers used to determine the confidence interval, usually expressed as "plus or minus x %". Note
 that the margin of error is computed on sample size and is only valid if the poll was welldesigned and executed on a
 true random sample. We guarantee it. A poll with misleading questions will produce misleading results.

Population
The larger group being studied. In political polls, the population is usually all eligible voters.

Random
 A way to choose a sample that represents all the people in the population we want to reach (in political polling,
 that's usually likely voters). A sample is random if each member of the population has an equal chance of being
 represented.

Reliability
Describes whether a measurement gives approximately the same result in repeated tests.

Sample
The number of people ( a proportion of the population )who were questioned.

Validity
Gauges whether a statistic measures what it is supposed to measure.

A Representative Sample.
Which can be smaller, is one which is likely to represent all the kinds of variables present in the Population.

stratified:
that is, it guarantees an accurate proportion of each variables that exist in the general population

