Suppose you drop a tennis ball from a height of 15 feet.

A random variable X with a probability density function () = {^-x > 0

Sliva [168]

The solutions to the questions are

The probability that X is between 2 and 4 is 0.314
The probability that X exceeds 3 is 0.199
The expected value of X is 2
The variance of X is 2

<h3>Find the probability that X is between 2 and 4</h3>

The probability density function is given as:

f(x)= xe^ -x for x>0

The probability is represented as:

$P(x) = \int\limits^a_b {f(x) \, dx$

So, we have:

$P(2 < x < 4) = \int\limits^4_2 {xe^{-x} \, dx$

Using an integral calculator, we have:

$P(2 < x < 4) =-(x + 1)e^{-x} |\limits^4_2$

Expand the expression

$P(2 < x < 4) =-(4 + 1)e^{-4} +(2 + 1)e^{-2}$

Evaluate the expressions

P(2 < x < 4) =-0.092 +0.406

Evaluate the sum

P(2 < x < 4) = 0.314

Hence, the probability that X is between 2 and 4 is 0.314

<h3>Find the probability that the value of X exceeds 3</h3>

This is represented as:

$P(x > 3) = \int\limits^{\infty}_3 {xe^{-x} \, dx$

Using an integral calculator, we have:

$P(x > 3) =-(x + 1)e^{-x} |\limits^{\infty}_3$

Expand the expression

$P(x > 3) =-(\infty + 1)e^{-\infty}+(3+ 1)e^{-3}$

Evaluate the expressions

P(x > 3) =0 + 0.199

Evaluate the sum

P(x > 3) = 0.199

Hence, the probability that X exceeds 3 is 0.199

<h3>Find the expected value of X</h3>

This is calculated as:

$E(x) = \int\limits^a_b {x * f(x) \, dx$

So, we have:

$E(x) = \int\limits^{\infty}_0 {x * xe^{-x} \, dx$

This gives

$E(x) = \int\limits^{\infty}_0 {x^2e^{-x} \, dx$

Using an integral calculator, we have:

$E(x) = -(x^2+2x+2)e^{-x}|\limits^{\infty}_0$

Expand the expression

$E(x) = -(\infty^2+2(\infty)+2)e^{-\infty} +(0^2+2(0)+2)e^{0}$

Evaluate the expressions

E(x) = 0 + 2

Evaluate

E(x) = 2

Hence, the expected value of X is 2

<h3>Find the Variance of X</h3>

This is calculated as:

V(x) = E(x^2) - (E(x))^2

Where:

$E(x^2) = \int\limits^{\infty}_0 {x^2 * xe^{-x} \, dx$

This gives

$E(x^2) = \int\limits^{\infty}_0 {x^3e^{-x} \, dx$

Using an integral calculator, we have:

$E(x^2) = -(x^3+3x^2 +6x+6)e^{-x}|\limits^{\infty}_0$

Expand the expression

$E(x^2) = -((\infty)^3+3(\infty)^2 +6(\infty)+6)e^{-\infty} +((0)^3+3(0)^2 +6(0)+6)e^{0}$

Evaluate the expressions

E(x^2) = -0 + 6

This gives

E(x^2) = 6

Recall that:

V(x) = E(x^2) - (E(x))^2

So, we have:

V(x) = 6 - 2^2

Evaluate

V(x) = 2

Hence, the variance of X is 2

Read more about probability density function at:

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<u>Complete question</u>

A random variable X with a probability density function f(x)= xe^ -x for x>0\\ 0& else

a. Find the probability that X is between 2 and 4

b. Find the probability that the value of X exceeds 3

c. Find the expected value of X

d. Find the Variance of X

7 0

2 years ago

Help!! I’m not smart.

Vadim26 [7]

Answer:

C. Reasons for changes in trends can be identified.

Step-by-step explanation:

The others would all be disadvantages.

7 0

3 years ago

Read 2 more answers

4. MAIL It cost Ramon $3.73 to mail a package to his grandmother. The post

Alex Ar [27]

Answer:

4 pounds

Step-by-step explanation:

First, I subtracted the cost of the first pound from the final product (3.73 - 2.38) and I got 1.35. I then divided the 1.35 by .45 (the 45 cents) to figure out how many more pounds the package was from the initial 1 pounds. 1.35/.45 is 3, plus the 1 pound from the beginning makes 4 pounds in total.

6 0

2 years ago

Represent √11.9 on the number line

ikadub [295]

The square root would be 3.4 if rounded to the tenths place

6 0

2 years ago

?In the table below, y is a linear function of x.X-214710y09182736What is the y intercept of the function

Aleonysh [2.5K]

y intercept : (0,6)

Explanation:

Use the formula:

. y = mx + b

Find m (the slope), using 2 random points of the graph: (-2,0) and (1,9)

. m = (y-y1) / (x-x1)

m = (0-9) / (-2-1)

m = -9 / -3

m = 3

Replace m in the equation:

. y = 3x + b

Find b by replacing y and x by a random point of the graph: (1,9)

. 9 = 3*1 + b

b = 9 - 3

b = 6

Replace b in the equation:

. y = 3x +6

To find the y-intercept replace x by 0 in the equation:

. y = 3*0 +6

y = 0+6

y = 6

=> y-intercept : (0,6)

7 0

1 year ago