Original sentence: 2n − 1 is both unbiased and has even odds of under/over estimation;.the unbiased estimate of N = 2n − 1 (taking n to be the population median) has equal odds of being an underestimate or an overestimate, regardless of the distribution of N (it is a nonparametric estimator, being an order statistic)
Edited sentence: 2m − 1 is both unbiased and has even odds of under/over estimation;.the unbiased estimate of N = 2m − 1 (taking m to be the population median) has equal odds of being an underestimate or an overestimate, regardless of the distribution of N (it is a nonparametric estimator, being an order statistic)