using said baseline sample to produce a new estimate Qi of said parameter Q at said time ti; and averaging Qi with said parameter's averaged estimate <Q>i???1 at the prior measurement time ti???1 to produce a value <Q>i of <Q> at time ti according to: ??? Q ??? i = N - 1 N ??? ( b ??? ??? Q ??? ( i - 1 ) ) + Q i N , where N is a constant and b corrects <Q> for its time variation between times ti a