Question

Given that X ~ B(n, p). If n = 10 and p = 0.4 then E(X) and Var(X) respectively are ______.

Options

• 4, 0.24

• 0.4, 0.24

• 4, 2.4

• 3, 0.24

Answer 1

Given that X ~ B(n, p). If n = 10 and p = 0.4 then E(X) and Var(X) respectively are 4, 2.4.

Explanation:

X ~ B(n, p)

Here, n = 10, p = 0.4

∴ q = 1 – p

q = 1 – 0.4

q = 0.6

E(X) = n × p

= 10 × 0.4

= 4

Var(X) = n × p × q

= 10 × 0.4 × 0.6

= 2.4