In statistical analysis, the Nth percentile measure is the value at which N% of the cases are at or below that percentile. For instance, for liver waiting list registrations in 1998, the 25th percentile for waiting time is 140 days. This means that by 140 days after being added to the liver-transplant waiting list, 25 percent of registrants had been transplanted. For the same group, the median for waiting time was 390 days. The median is defined as the 50th percentile. For this group of liver registrants, 50 percent had been transplanted by 390 days.