If the question was about the batting performance of the two players in that particular series, then do we not have all the scores in the population?

We have it, they will be introduced in the hands on part.

@Ishvinder my question is whether its a population and not a sample? In which case the notation should have been Mu and Sigma as opposed to m and s.

No, it’s a sample… the population would be scores of root and cook for all of their matches.

@sgnana’s question is that if we are talking about a particular series, then will the data not be population, rather than a sample? Since the data is specific to a series, how is this a sample?

I think even if we consider just the series data, there would have been many batsmen in the complete series data. But we’re talking about cook and root, this way we can term it a sample.