The UK reach and frequency model

Date of publication: June 15, 1992

Author: Steve Wilcox

Abstract:

The basis of a reach and frequency analysis is a count of the number of commercial spots seen by each individual in an advertising schedule. When this analysis is constructed from a people meter panel that reports on a daily basis, the obvious start point is to extract the sample of continuous reporters. This is defined to be the sample of individuals from whom a valid record of viewing was received for at least every day on which a spot in the schedule was transmitted. It is only for those individuals that we can construct a complete account of which spots they did or did not view. This was the standard approach adopted within the BARB Television Audience Measurement System in the UK prior to the launch of the new service in August 1991. However, this meant that users were forced to live with potential shortfalls in data quality and certain practical difficulties: -The continuous sample base decreases as the length of the schedule increases. A loss of 1% or 2% of the panel each day can easily compound to a loss of 10% to 20% over a four week campaign. Sampling errors would increase and there is potential for bias in the continuous sample. The demographic weighting of every continuous panel to target population profiles is not a practical option given a large number of reach and frequency analyses required on a very fast turn-around. Guest viewing could not be incorporated into the reach and frequency analysis because there was no such thing as a continuous panel of guest viewers. In fact, this would probably not be meaningful because, in the context of reach and frequency, guest viewing is really a surrogate measurement of panel members viewing in other (un-metered) households. Given the problems above, reach and frequency analyses could never be consistent with the published currency which estimated individual spot audiences from the full daily reporting samples, using a more sophisticated calculation procedure and incorporating guest viewing. The introduction of the new BARB Television Audience Measurement Panel last year created a requirement for change and an opportunity to re-visit the issues listed above.

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