(a) You must use the ratio of sample total PMT over sample total PPMT as the sample ratio.
(b) For estimating annual total PMT:
(1) Use sample PMT/PPMT ratio for the entire sample if you do not group your service.
(2) Use sample PMT/PPMT for each group if your sampling plan is based on grouping.
(c) For estimating average daily PMT by type of service days, use the sample PMT/PPMT ratio by type of service days.