This is analogous to the idea of expected values not being possible values. Although we can't actually see, e.g., 2.5 reads with a given allele, it makes sense to have the expected number of occurrences of a given allele (i.e. the average) to be 2.5.
This is analogous to the idea of expected values not being possible values. Although we can't actually see, e.g., 2.5 reads with a given allele, it makes sense to have the expected number of occurrences of a given allele (i.e. the average) to be 2.5.