Question 1119938
By Using Binomial Distribution
Formula (nCx)*[(p)^x]*[(q)^n-x]
In this Problem Prob. of Success is 0.5 and Prob. of Failure is also 0.5
Remember that  p+q=1
So Question is Find Prob. of Correct Question is 8 or Less than 8
Stepwise Solution
P(x=0)=20C0*0.5^0*0.5^20=1/1048576
P(x=1)=20C1*0.5^1*0.5^19=5/262144
P(x=2)=20C2*0.5^2*0.5^18=95/524288
P(x=3)=20C3*0.5^3*0.5^17=285/262144
P(x=4)=20C4*0.5^4*0.5^16=4.621*10^-3
P(x=5)=20C5*0.5^5*0.5^15=969/65536
P(x=6)=20C6*0.5^6*0.5^14=0.03696
P(x=7)=20C7*0.5^7*0.5^13=4845/65536
P(x=8)=20C8*0.5^8*0.5^12=0.1201
Sum up All the Answers>>>>>=0.2475