Statistics and Probability Dictionary
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Margin of Error
The margin of error expresses the maximum expected difference between the true population
parameter and a sample estimate of that parameter. To be meaningful, the margin
of error should be qualified by a probability statement (often expressed in
the form of a
For example, a pollster might
report that 50% of voters will choose the Democratic candidate. To indicate the
quality of the survey result, the pollster might add that the margin of error
is +5%, with a confidence level
of 90%. This means that if the survey were repeated many times
with different samples, the true percentage of Democratic voters would
fall within the margin of error 90% of the time.