Answer:
a) 8*88*10⁻⁶ ( 0.00088 %)
b) 0.2137 (21.37%)
Step-by-step explanation:
if the test contains 25 questions and each questions is independent of the others, then the random variable X= answer "x" questions correctly , has a binomial probability distribution. Then
P(X=x)= n!/((n-x)!*x!)*p^x*(1-p)^(n-x)
where
n= total number of questions= 25
p= probability of getting a question right = 1/4
then
a) P(x=n) = p^n = (1/4)²⁵ = 8*88*10⁻⁶ ( 0.00088 %)
b) P(x<5)= F(5)
where F(x) is the cumulative binomial probability distribution- Then from tables
P(x<5)= F(5)= 0.2137 (21.37%)
