Confidence
Confidence is a measure of certainty regarding observations and calculations of data.
Confidence can be expressed as an interval and/or level:
Confidence Interval - expresses a range of certainty
Confidence Level - expresses a specific probability of certainty
An Example
An auto manufacturer runs city driving tests on a new model to determine the average mileage per gallon (mpg) of gas efficiency it will advertise. The tests and measurements result in a measured value with a confidence interval and a confidence level that the value and interval are correct: