Strictly Come Dancing is Strictly Unfair

Jen Rogers is a statistics researcher and lecturer on the College of Oxford.

We chat about how the scoring system works on Strictly Come Dancing (“Dancing With the Stars” within the USA and different international locations). The UK system for coping with ties is unfair!

Jen and I do Maths Inspiration exhibits collectively.

We’re out doing The Curious Coincidence of Maths within the Daytime in Melbourne subsequent February.

Outcomes from Judges votes Saturday 2 December 2017

Joint first: Alexandra & Gorka
Joint first: Debbie & Giovanni
Second place: Joe & Katya
Third place: Mollie & AJ
Joint final: Gemma & Aljaž
Joint final: Davood & Nadiya

After being mixed with the viewers rankings the underside two have been Alexandra & Gorka and Davood & Nadiya. But when the ties have been finished correctly that might have been Gemma & Aljaž as an alternative of Alexandra & Gorka.

When you have a option to get us the info from the BBC, ship me an nameless e-mail!

– Shimassi and others have made essential factors about how this technique favours the general public vote. As a result of a tie means the judges by chance give additional factors to the contestants they’re attempting to rank on the backside.

That is my fault for not being clear sufficient. After we mentioned issues like “skewing it in the direction of the judges” and “inflating the judges’s rating” we’re speaking about there being extra factors being given. Not that the judges have been getting their approach. Sorry I did a foul job of speaking about that and my language was not exact sufficient.

Jen’s important instance was that the contestant ranked prime by the judges was unfairly moved to the underside two (and into the dance-off) as a result of the general public acquired their approach.

Briefly: the viewers can all the time penalise somebody by given them one vote, the judges can’t all the time try this.

One other fascinating equity metric is that somebody top-ranked by the judges and bottom-ranked by the viewers ought to be precisely equal to somebody bottom-ranked by the judges and top-ranked by the general public. But when there’s a tie for the judges the viewers selection will get an unfair benefit.

– Others have identified (and David Heath despatched an ideal e-mail to me) that Strictly as soon as had a system like what we describe however they acquired into bother as a result of individuals have been paying to telephone in and vote for a contestant when it was mathematically inconceivable for them to be voted out of the dance-off. And the BBC can’t have a phone-in competitors if some votes can’t make a distinction.

This makes for an fascinating set of standards. The voting system must be truthful, simple to clarify to a TV viewers and the viewers vote is all the time capable of transfer any given contestant out of the underside two.

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