Assume that source data is entered in A 1~A4 1 and B 1.
=AVERAGE(OFFSET(A$ 1,RAND()*40,),OFFSET(A$ 1,RAND()*40,),OFFSET(A$ 1,RAND()*40,)
Input and fill it down to B4 1 (assuming);
Column b is the average value of "temporarily saved"
Enter at C 1
= mode (B 1:B4 1)
Get into the car.
This is the number with the highest average probability you want.
Press F2 and Enter alternately to update the data.