Mean, or average The sum of a measurement, divided by the number of contributors to that measurement. The sample size, generally the number of people questioned in a poll. The larger group being studied. In political polls, the population is usually all eligible 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.
The percentage of the originally identified sample that finally responds to the survey. The number of people who were questioned. An error derived from a mistake in sampling procedure. A statistical number that gauges how far any one measurement is likely to vary from the mean. An error or bias introduced by some methodological error.