  The quality of space-time earthquake prediction is usually characterized by a
two-dimensional error diagram (n,tau), where 'n' is the rate of
failures-to-predict and 'tau' is the normalized measure of space-time alarm.
The most interesting space measure for analysis of a prediction strategy is the
rate of target events m(dg) in a sub-area 'dg'. In this case the quantity
H=1-(n+tau) determines the prediction capability of the strategy. The
uncertainty of m(dg) causes difficulties in estimating 'H' and the statistical
significance, 'alfa', of prediction results. We investigate this problem
theoretically and show how the uncertainty of the measure can be taken into
account in two situations, viz., the estimation of 'alfa' and the construction
of a confidence zone for (n,tau)-parameters of the random strategies. We use
our results to analyse the M8 earthquake prediction algorithm.
