County Coverage Reliability Estimates

Reliability estimates for the 2011 Radio County Coverage are available for all counties located within County Coverage reporting areas. These reliability estimates quantify the amount of sampling error associated with the estimates Arbitron produces.

The reliability of a survey estimate is generally defined in terms of the estimated margin of sampling error around the estimate, or confidence interval. The confidence interval describes the extent to which a survey estimate, based on a random sample of the universe, may vary from the result that would be obtained through a complete census.

Using the application provided, a user can calculate an estimated standard error for any 2011 County Coverage rating. This standard error can then be used to create a confidence interval around the rating. Below are the calculations necessary to create intervals at a few customary confidence levels.

For example, a station has a cume rating of 12.0 in County A. If this station has a standard error of 0.6, a 90% confidence interval around that rating would be 11.0 to 13.0, which is 12.0 +/- (1.645 x 0.6). This means that the user can be 90% confident that a survey of all persons 12+ in County A would yield a cume rating between 11.0 and 13.0.

To calculate reliability estimates, click here