AMPS Rating (AR)

An AMPS Rating is the proportion of viewers, averaged across some time period (a commercial spot or break, a quarter-hour or a programme) and percentaged on the total number of individual panel members in the relevant group (eg. 'all adults' or 'females').

ARs are calculated by summing the products of numbers of viewers and relevant times spent viewing (within the period concerned) and dividing by the product of the total number of potential viewers and the length of the period concerned. An AR is thus, in effect, a time-weighted average of audience size, indicated by an index which varies between 0 and 100. However, because visitors are included, a maximum AR greater than 100 is theoretically possible as visitors are not included in the base. Theoretically, visitors to metered households compensate in part for panel members who view in non-metered homes. Informant numbers in the tables exclude visitors. No visitors are classified as main purchasers.

Whilst the AMPS Meter scans the status of sets and individuals at a rate of approximately 16 times in 30 seconds or at roughly two-second intervals, any viewing session of less than about 20 seconds duration is ignored by the Meter and therefore forms part of the AR calculations for the station beinq viewed prior to such a brief change.

At present, all weekly report ARs relate to real time, off-air viewing only; the deferred viewing of a taped programme, at some later date, is excluded. However, a sample of VCR homes have had their VCR's 'Fingerprinted' to enable measurement of taped viewing - this is examined from time to time.

For clarification, an example of how ARs are calculated for a 15 minute time period is as follows:

If the universe is 200, then the AR = 15.00/200 = 7.5 (rounded to 8 in the report).