Two days before an election, city officials projected that 67% of all registered voters would vote. Two days after the election, after reviewing the actual voting turnout, they announced that 81% of registered voters had actually voted. Which of these percentages is a parameter, and which is a statistic?
67% is a statistic and 81% is a parameter.
A statistic tries to estimate something about the population- in this case, the statistic is estimating the percentage of registered voters that vote in the election. A parameter is the value that the statistic is trying to estimate- the actual percentage of registered voter support that showed up on Election Day.