(a) A sample ratio is the ratio between the sample total of one measure of service-consumed and the sample total of another measure of service-consumed. This *Sampling Manual* uses two sample ratios:

(1) The ratio of sample total PMT over sample total UPT gives the sample APTL.

(2) The ratio of sample total PMT over sample total PPMT gives the sample PMT/PPMT ratio.

(b) They may be calculated for the entire annual sample or by the type of service days.