Question 1187690
p=0.05
for exactly 2 it is 72C2*0.05^2*0.95^70=0.1763
for fewer than 4, calculate 3, 2,1,0
for 3 it is 0.2165
for 1 it is 72C1*0.05*0.95^71=0.0943
for 0 it is 0.95^72=0.0249
Those 4 add to 0.5120
on the calculator, use binomcdf(72,0.05,3) and get 0.5119. The difference is in rounding, since the exact answer to more decimal places is 0.51194967, which barely fails to meet the rounding criteria to 0.5120.