Step-1

Title: Continuous random variable

Grade: 9-a Lesson: S4-L7

Explanation: Hello Students, time to practice and review the steps for the problem.

Lesson Steps

Step Type Explanation Answer

1

Problem

Consider a andom variable X with probability density function \$f(x) = \begin{cases} 4x^3,for & 0≤x≤1 \\ 0,& otherwise \\ \end{cases}\$.Find mean and variance.

2

Formula:

E(X) = \$\int_-\infty^\infty\$x f(x)dx

3

Step

Substitute f(x) in the formula

E(X) = \$\int_0^1 x 4x^3\$ dx

4

Step

Simplification

E(X) = 4 \$(x^5/5)_0^1\$

5

Step

After simplification

\$E(X) = 4/5\$

6

Formula:

\$E(X^2)[\int_-\infty^\infty x^2\$ f(x)dx

7

Step

Substitute f(x) in the formula

E(X) = \$\int_0^1 x^2 4x^3\$ dx

8

Step

Simplification

\$E(X^2) =\int_0^1 4x^5\$ dx

9

Step

Simplification

\$E(X^2) =4(x^6/6)_0^1\$

10

Step

After simplification

\$E(X^2) = 4/6\$

11

Formula:

V(X) = \$E(X^2) - (E(X))^2\$

12

Step

Simplification

V(X) = \$4/6 - (4/5)^2\$

13

Step

After simplification

V(X) = \$4/6 - 16/25\$

14

Step

After simplification

V(X) = \$2/75\$

15

Answer

D

Tutor: Questions

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1

Problem

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2

Clue

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3

Hint

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4

Step

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5

Step

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