West Ham v Aston Villa kick off 2000 Sky Sports Main Event / Sky Sports Premier League / Sky Sports Ultra HD


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Do you actually know what a margin of error is, or a confidence interval?

Of course I do. I think it's quite endearing that you think it's a concept that some people might not understand. It's pretty basic. You are factoring in a predetermined distance from the last man that allows for error. Within that area the infield decision stands. It's a concept that is easy to understand. The problem that you have is failing to consider its application. There will be controversy relating to whether a decision falls within the margin of error or not. I understand that it adds certainty to the offside but there are two scenarios that will make it unworkable...

1) A player is a mm outside the margin of error (101cm) but the goal is given. The flag hasn't gone up. The goal is chalked off. They will be bringing up the same toenail stuff we are hearing now.

2) You will get two scenarios in the same game.

a) A team have a goal allowed even though an attacker is 90cm offside.
b) The other team have a goal disallowed where the player is 1cm offside.

Cue massive crying about consistency and how it's not fair, as we have the technology to make it more consistent. There'd be meltdowns left, right and centre.

I'm fine with you disagreeing with me but I think you are getting frustrated and being a bit condescending because you don't understand what I'm saying. I think my 3 year old could tell you what a margin of error is.
 
Of course I do. I think it's quite endearing that you think it's a concept that some people might not understand. It's pretty basic. You are factoring in a predetermined distance from the last man that allows for error. Within that area the infield decision stands. It's a concept that is easy to understand. The problem that you have is failing to consider its application. There will be controversy relating to whether a decision falls within the margin of error or not. I understand that it adds certainty to the offside but there are two scenarios that will make it unworkable...

1) A player is a mm outside the margin of error (101cm) but the goal is given. The flag hasn't gone up. The goal is chalked off. They will be bringing up the same toenail stuff we are hearing now.

2) You will get two scenarios in the same game.

a) A team have a goal allowed even though an attacker is 90cm offside.
b) The other team have a goal disallowed where the player is 1cm offside.

Cue massive crying about consistency and how it's not fair, as we have the technology to make it more consistent. There'd be meltdowns left, right and centre.

I'm fine with you disagreeing with me but I think you are getting frustrated and being a bit condescending because you don't understand what I'm saying. I think my 3 year old could tell you what a margin of error is.

There is a clear misnomer in your assumptions though. Let me replace it for you

a) A team have a goal allowed even though an attacker is 90cm offside IN ONE RANDOM STILL IMAGE TAKEN SOMEWHERE AROUND THE POINT THE BALL IS PLAYED
b) The other team have a goal disallowed where the player is 1cm offside IN ONE RANDOM STILL IMAGE TAKEN SOMEWHERE AROUND THE POINT THE BALL IS PLAYED

There is no factual on or offside being displayed. The VAR technology is good enough to show that a player is 1cm offside IN THE GIVEN IMAGE. I am not disputing that. So the toenail stuff is pointless and a stupid argument made by simpletons. The problem is that the image used is 100% likely to not be the exact moment to the nearest nanosecond that the ball is played, therefore the decision cannot be made from that still image. All you can do is calculate the standard deviation on this error and apply a confidence interval that you are happy with.

Let's assume that there is a standard deviation of 5cm for arguments sake. Then in the case of one offside call showing the player is 5cm offside by the still image used, then the probability of the player actually being offside is 69.3%. If the player is 10cm offside in the still image, then the probability of him being offside is just short of 90%. At 15cm, this extends to 99%.

In the case of last nights decision, lets say he was 2cm offside - that would equate to a probability of actually being offside of around 58%. Is that really accurate enough to overturn the on-field decision?

Lets reduce that down to the 8mm that Sky claimed Mane was offside in the Merseyside Derby. With a 5cm standard deviation assumed then that decision would be 53% accurate.

Do you see the problem now? It's barely anymore accurate than tossing a coin, which would by definition be 50% accurate. I'm 100% certain that if you sampled all linesmen decisions for offsides between 0-2cm offside you would have an accuracy rate higher than 58% - hell you would get 50% by pure guessing.

The standard deviation of the error is easily calculable by an error analyst, so that could be determined fairly simplistically with the required technical data, such as camera specifications. Then you would need to determine an appropriate confidence interval - you'll never get it 100% accurate, that does not exist, but 99% accuracy (i.e. an error margin of 3 standard deviations) would be more than acceptable - could even get away with 90% accuracy (i.e. an error margin of 2 standard deviations).

Note - all calculations were done without a calculator, so might be off by a percentage point, for the pedants of the board.
 
There is a clear misnomer in your assumptions though. Let me replace it for you

a) A team have a goal allowed even though an attacker is 90cm offside IN ONE RANDOM STILL IMAGE TAKEN SOMEWHERE AROUND THE POINT THE BALL IS PLAYED
b) The other team have a goal disallowed where the player is 1cm offside IN ONE RANDOM STILL IMAGE TAKEN SOMEWHERE AROUND THE POINT THE BALL IS PLAYED

There is no factual on or offside being displayed. The VAR technology is good enough to show that a player is 1cm offside IN THE GIVEN IMAGE. I am not disputing that. So the toenail stuff is pointless and a stupid argument made by simpletons. The problem is that the image used is 100% likely to not be the exact moment to the nearest nanosecond that the ball is played, therefore the decision cannot be made from that still image. All you can do is calculate the standard deviation on this error and apply a confidence interval that you are happy with.

Let's assume that there is a standard deviation of 5cm for arguments sake. Then in the case of one offside call showing the player is 5cm offside by the still image used, then the probability of the player actually being offside is 69.3%. If the player is 10cm offside in the still image, then the probability of him being offside is just short of 90%. At 15cm, this extends to 99%.

In the case of last nights decision, lets say he was 2cm offside - that would equate to a probability of actually being offside of around 58%. Is that really accurate enough to overturn the on-field decision?

Lets reduce that down to the 8mm that Sky claimed Mane was offside in the Merseyside Derby. With a 5cm standard deviation assumed then that decision would be 53% accurate.

Do you see the problem now? It's barely anymore accurate than tossing a coin, which would by definition be 50% accurate. I'm 100% certain that if you sampled all linesmen decisions for offsides between 0-2cm offside you would have an accuracy rate higher than 58% - hell you would get 50% by pure guessing.

The standard deviation of the error is easily calculable by an error analyst, so that could be determined fairly simplistically with the required technical data, such as camera specifications. Then you would need to determine an appropriate confidence interval - you'll never get it 100% accurate, that does not exist, but 99% accuracy (i.e. an error margin of 3 standard deviations) would be more than acceptable - could even get away with 90% accuracy (i.e. an error margin of 2 standard deviations).

Note - all calculations were done without a calculator, so might be off by a percentage point, for the pedants of the board.

OK I can see what you're saying. The problem is that the 'footballing fraternity' won't care about these calculations. They'll see the same technology being used and seeing the same frames applied to different scenarios and allowing one goal to stand where another goal with a frame showing a much tighter decision being disallowed. The clamour for consistency will return.

The only way I can see, that is fair, is to measure foot position. I'm pretty sure that would do away with the vast majority of these slide rule decisions that are upsetting people.
 
OK I can see what you're saying. The problem is that the 'footballing fraternity' won't care about these calculations. They'll see the same technology being used and seeing the same frames applied to different scenarios and allowing one goal to stand where another goal with a frame showing a much tighter decision being disallowed. The clamour for consistency will return.

The only way I can see, that is fair, is to measure foot position. I'm pretty sure that would do away with the vast majority of these slide rule decisions that are upsetting people.

Would drawing a line, say an inch wide between players not work though? Yes, it'll give the attacker the advantage but it may also encourage centre halves to defend properly again - something we're increasingly seeing precious little of (particularly in this country)
 
Yep stupidly close but Undeniably offside
And let’s be fair without the single worst VAR decision ever seen Villa would be in the championship now so they can hardly complain
Except that they did a summary of all the VAR errors and most teams didn't move much on the table at all, inclusive us. We would have stayed up if VAR did all the right calls either way.
 
Would drawing a line, say an inch wide between players not work though? Yes, it'll give the attacker the advantage but it may also encourage centre halves to defend properly again - something we're increasingly seeing precious little of (particularly in this country)

Basically the artistic representation of the error margin I proposed then?
Could was said at the time

Well clearly yes as we all saw them within seconds

It’s a tough ask to get the VAR to overrule the Hawkeye
 
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