Third, different analytic techniques may increase readmission's descriptive power. The authors used dichotomous models that assign all readmissions equal weight, but 40% (N=18 of 45) of their study group's readmissions occurred within the first 30 days of a 6-month follow-up. Statistical methods that incorporate person-time, such as Poisson distribution or proportional hazards regression, can indicate factors that cause faster readmission. For example, one factor causing readmission on day 5 of follow-up is clearly more harmful than another causing readmission on day 30. Assigning the outcomes equal weight could bias results toward the null.