The Appreciation Index or AI is a measure of how much the audience enjoyed the programme. The score, out of a hundred, is compiled by a specially selected panel of around 5,000 people who go online and rate and comment on programmes.
This episode's score of 82 is at the lower end of the range for this series so far but is nevertheless a solid score for the show, putting it equal with The Girl Who Died and one point higher than The Woman Who Lived.
The AI scores for Series 9 so far are as follows:
The Magician's Apprentice & Under the Lake - 84
The Witch's Familiar & Before the Flood - 83
The Girl Who Died & The Zygon Invasion - 82
The Woman Who Lived - 81
Doctor Who finished as the 46th most watched programme of the week with an average of 3.87 million viewers, a figure that is set to rise once consolidated figures are released next week.
[Source: Doctor Who News]