Efficiency definition (cont.)
probability to find 4 HOTs when 4 expected ~ ef4 ez4 ecomb4
probability to find 3 HOTs + F hit for the 4th ~ 4 ef4 ez3(1-ez ) ecomb3
probability to find 3 HOTs + Z hit for the 4th ~ 4 ez4 ef3(1-ef ) ecomb3
probability to find 3 HOTs + neither F nor Z strips for the 4th
~ 16 ez3 ef3(1-ef ) (1-ez ) ecomb3
probability to find 3 HOTs + both F and Z strips for the 4th which are not combined into the space point ~ 4 ez4 ef4 ecomb3(1 - ecomb)