Individuals are the measuring units of radio rating. These estimates are generally based on audience surveys. The limited count of audiences taken into sampling in ratings surveys accurately represents the larger audience base only if the methods of the survey are statistically valid.
Radio programmes are divided into several day parts. These day parts, which differ from station to station, are used for estimating the rating. There are survey areas such metro survey are (MSA), total survey area (TSA) which comes under the purview of rating. Cumulative (CUME) or Average quarter hour (AQH) are used as radio rating metrics.
Time spent listening (TSL), a listener loyalty metric is measured by the following formula:
Time Spent Listening (TSL)= Number of Quarter Hours × AQH / CUME