The probability distribution of the random variable X is given by the formula P(X = x) = 0.09+0.01x^2 for x= 1,2,3,4,5 ). Find E(X).

The expected value of a discrete variable is defined as:

E(X) = ∑x*P(X=x) (for all possible values of x, in this case x = {1,2,3,4,5} ) 

(next, we will expand the summation and substitute in the values given, we are able to find P(X=x) simply by substituting in the equation from above)

= 1*(0.09+0.011^2) + 2(0.09+0.012^2) + 3(0.09+0.013^2) + 4(0.09+0.014^2) + 5(0.09+0.01*5^2)

(next, we will factorize in order to make calculation easier and less prone to mistakes)

= 0.09(1+2+3+4+5) + 0.01*(11^2 + 22^2 + 33^2 + 44^2 + 5*5^2)

(next, we will add up the first bracket and simplify the second bracket)

= 0.09*(15) + 0.01*(1^3 + 2^3 + 3^3 + 4^3 +5^3)

(next, we will multiply through the first bracket and multiply the individual expressions in the second bracket)

= 1.35 + 0.01*(1 + 8 + 27 + 64 + 125)

(next, we add up the second bracket)

= 1.35 + 0.01*(225)

= 1.35 + 2.25 = 3.6

E(X) = 3.6 (the expected value of X is 3.6)

RH
Answered by Robin H. Maths tutor

7648 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

Integration of ln(x)


How do you know if a function is odd or even?


Find the integral between 1 and -2 for (4-x^2-3x^3)


A stone is thrown from a bridge 10m above water at 30ms^-1 30 degrees above the horizontal. How long does the stone take to strike the water? What is its horizontal displacement at this time?


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2026 by IXL Learning