"An increase of number of escort vessels from 6 to 9 led to a reducton of losses by about 25 per cent."
where L is the number of Losses and E is the number of escort vessels.
"An increase of size from an average of 32 to 54, was associated with a decrease of fractional losses (i.e. ships sunk/ships sailed) from 2.5% to 1.1%, i.e. a reduction of losses of 56 %."
where L is again the number of Losses and S is the size of the convoy.