The Appreciation Index (AI) figure is a measure of how much the audience enjoyed the programme. The score is out of 100 and is compiled by a specially selected panel of around 5,000 people who go online to rate and comment on programmes.
The AI score of 87 meant that Doctor Who scored higher than most of Saturday’s programmes. Casualty had 87, Richard Briers: A Tribute had 88 and Easter From Kings had a score of 89.
[Source: Doctor Who News Page]