The Law Of Large Numbers and the Law Of Averages

Everyone is familiar with the Law Of Averages and most with theproblems incorrect application can cause. However , less arefamiliar with the Law Of Large Numbers.For those fully conversant with the rightsand wrongs of the Law Of Averages , feel
The Law Of Large Numbers and the Law Of Averages
Darren Brett
Darren Brett Tipster Competition Manager

Horse Racing, greyhounds and snooker specialist with thirty years experience of writing about sport across multiple platforms. A QPR and Snooker fan

Everyone is familiar with the Law Of Averages and most with the problems incorrect application can cause. 

However, less are familiar with the Law Of Large Numbers.

Betting systems and strategies are often based on averages and all have numbers at their heart.   

For those fully conversant with the rights and wrongs of the Law Of Averages, feel free to skip the examples below.

Example 1

I shall use the old chestnut of the coin toss ( using an unbiased coin ).


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The true odds of a head or tail are evens," yet some people still believe that because 3 heads have appeared consecutively that the next toss is more likely to be a tail than a head, it is not.


Example 2


A slightly different ( but progressive ) analogy is drawing a card from a fresh deck of cards.

If a full deck of cards is used each time, the chance of a red or black card appearing is again equal and the Law Of Averages is doomed.


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If the same deck is used and 3 red cards have been drawn in a row, people may still say the Law Of Averages dictates that the next card is more likely to be black than red - indeed it is!
 
However, it has nothing to do with the Law Of Averages. It is simply a case that there are now more black cards available than red. 

In the extreme case of the first 26 cards being red, the next is Guaranteed to be black.


Example 3


A final example to blow the theory out of the water, I'll take a race meeting this time. 


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About 30% of favourites win and on a particular day, no favourite has won any of the first 6 races. 

Our law states that a favourite is long overdue by the time it comes to the final race, but only a fool would apply that equally to a 4/6 chance in a 4 runner affair at Wolverhampton and a 10/1 the field handicap at Ascot. Similarly, with a 6 or 7 race card on the horses, 2 favourites winning is the par result. 


Any number from none to all can win on a given day and maybe on the next 2 or 3 days, but neither extreme can continue throughout the season.

The Law Of Large Numbers

Returning to the coin toss, the Law Of Averages would ( correctly ) dictate that for any four coin tosses, the most likely result would be for 2 heads to appear once, 2 tails to appear once and one of each to appear twice ( the order being irrelevant ).

That is no more than a case of calculating probabilities, but there again, what else is the Law Of Averages actually based on?

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The Law Of Large Numbers in a way both proves and more importantly disproves the Law Of Averages.

Whilst more accurate than the Law of Averages, by definition the examples involve the longer term and therefore larger numbers.

With 4 tosses of the coin, it is likely that the result will be as above because it is the most likely outcome, but no other combination would be a surprise. 

With 4000 such examples, it remains that the split will be approximately 1000 instances of 2 heads, 1000 of 2 tails, and 2000 mixed.

The major difference now is that the Law Of Large Numbers states that this exact distribution is unlikely to occur but that the larger the sample, the closer to this figure in % terms the results will get.

In a jargon-free zone the distribution maybe like this. 

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H will mean 2 heads, T means 2 tails and M stands for a mixture.

After 20 tosses H=4, T=7, M=9. 

In percentage terms 20, 35, and 45.

After 100 tosses H=23 , T=29 , M=48.

Percentages are obvious but it should be noted that although getting closer to 25, 25, and 50 the gap between H and T is now double what it was before.

The Law Of Large Numbers suggested this could happen whilst getting closer to the par figures whereas the Law Of Averages would have expected more H than T in the second sample to compensate for the difference in the first.

After 1000 tosses the Law Of Large Numbers will expect the figures to be even closer but although they may be split H=250, T=250 and M=500 it states that this is still a very unlikely result.

Summary

The Law Of Averages says something will happen very soon if not immediately whereas the Law Of Large Numbers expects the correction to take place over a longer period. 


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The Law Of Averages can be used to calculate the most likely result of a one-off action, not connected to any previous or subsequent result. 

As seen earlier, this is no more or less than an incorrect interpretation and or application of percentages or statistics.

The Law Of Large Numbers says that whatever the situation, over a long period the results will get closer to the percentage expectations as more results are known but because of the potentially huge numbers involved may never reach the perfect figure.

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