What is statistics and why is it relevant to rugby?

Intro

In short, (formal) statistical analysis (like we do) is relevant to rugby as it can help explain what is going on.  It allows one to go beyond pure opinion (which may be right or wrong…) and bring objectivity.

Example: “tradition is really important in rugby”…..an opinion

“following testing on historic RWC data, we can say with a high (statistically a 90%+ degree of confidence) that tradition (as measured empirically by the number of years since a country started playing rugby) part explains how far a country advanced in the RWCs going back to 1987.”…… that’s empirical insight, we’re trained econometricians (economic statisticians) and thats what we do.

What is Statistics ?

Many moons ago someone in ancient Greece had a great insight.

Suppose you wanted to know what was going on in a state (remember they were city states back then).  You could ask the entire population of the city state; but that would be very costly and time consuming.  One practical alternative would be to ask a sample of the population.  Clearly, this would be cheaper and faster.  The idea of taking a sample is that it can be generalised to represent the population – hence the term ‘stat’istics.

Huge care needs to be taken, however, with sample selection.  For example, one could ask 1 million 25 years olds, but that would only give a good view on what 25 year olds think.  What then what about older or younger groups ?  There would be no information about them from the sample taken. So the sample would not be representative of the population and any wider inferences drawn would be highly unlikely to be reliable.

Statisticians know that the quality of their output depends on the sample size, random selection and ideally the representative characteristics within that population.   So you will often see that e.g. political opinion polls are based on random draws from samples of x thousand people representative of the broader population….

Subject to the above, one can then perform what is known as statistical inference – that is, one can start to infer characteristics of the population based on the results of the sample (subject to confidence bands, sometimes called margins of error).

Link to Sports and Rugby

The idea was then applied to sports.  Collect data on games, run some statistical analysis, perform inference and interpret the results….

This is what we do (recognising always that there can be sampling constraints, e.g. there have only been seven editions of RWC held to date, in sampling terms, seven is a small number).  That means that caution must be taken in terms of any generalisations….

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Empirical Rugby

Empirical Rugby is a blog that provides fundmental insight into rugby union using empirical analysis of rugby data.

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