 As the population is unknown, the true error in a sample statistic against its population value is unknown.In bootstrap-resamples, the 'population' is in fact the sample, and this is known; hence the quality of inference of the 'true' sample from resampled data (resampled → sample) is measurable.More formally, the bootstrap works by treating inference of the true probability distribution "J", given the original data, as being analogous to inference of the empirical distribution "Ĵ", given the resampled data.