A TV newscaster reports the results of a poll of voters, and then says, "The margin of error is plus or minus 1%." Explain carefully what that means.
The proportion of the population who voted for one candidate is 1% less than the percent of the population who voted for the other candidate.
The true proportion is within 1 % of her estimate, with some degree of confidence.
It means that 1 % of the polls are invalid.
The sample proportion is within 1% of her estimate, with some degree of confidence.