Try the fastest way to create flashcards
Question

Decide whether each function defined as follows is a probability density function for the given interval. f(x)=xf(x)=\sqrt{x}; [4, 9]

Solution

Verified
Answered 6 months ago
Answered 6 months ago
Step 1
1 of 2

The function f(x)f(x) is given to us as :

f(x)=x;x[4,9]f(x) = \sqrt{x}\quad ;\quad x\in [4, 9]

To check whether it is a pdf or not, we first recall the conditions for a function to be a probability density function.

Conditions for function to be a pdf :\textbf{Conditions for function to be a pdf :}

The function ff is a probability density function of a random variable XX in the interval [a, b] if it satisfies following two conditions :

Condition 1 : f(x)0f(x)\ge 0 for all xx in the interval [a, b]

Condition 2 : abf(x)dx=1\int_{a}^{b}f(x)\cdot dx = 1

As we can see that f(x)0f(x)\ge 0 for all xx in the interval [4,9][4, 9] , hence it satisfies condition-1

Now we check for condition-2 :

49f(x)dx=49xdx=[x3/23/2]49Since pqxndx=[xn+1n+1]pq=(23)[x3/2]49=(23)[93/243/2]=(23)[278]49f(x)dx=3831\begin{align*} \int_{4}^{9}f(x)\cdot dx &= \int_{4}^{9}\sqrt{x}\cdot dx\\ &= \left[\dfrac{x^{3/2}}{3/2}\right]_{4}^{9}\qquad\qquad\qquad\qquad\text{Since } \int_{p}^{q} x^{n}\cdot dx = \left[\dfrac{x^{n+1}}{n+1}\right]_{p}^{q}\\ &= \left(\dfrac{2}{3}\right)\left[x^{3/2}\right]_{4}^{9}\\ &= \left(\dfrac{2}{3}\right)\left[9^{3/2} - 4^{3/2}\right]\\ &= \left(\dfrac{2}{3}\right)\left[27 - 8\right]\\ \int_{4}^{9}f(x)\cdot dx &= \dfrac{38}{3} \ne 1 \end{align*}

Since it does not satisfy condition-2, hence f(x)f(x) is not a probability density function on the indicated interval.

Create a free account to view solutions

Create a free account to view solutions

Recommended textbook solutions

Thomas' Calculus 14th Edition by Christopher E Heil, Joel R. Hass, Maurice D. Weir

Thomas' Calculus

14th EditionISBN: 9780134438986 (11 more)Christopher E Heil, Joel R. Hass, Maurice D. Weir
10,142 solutions
Calculus with Applications 11th Edition by Margaret L. Lial, Nathan P. Ritchey, Raymond N. Greenwell

Calculus with Applications

11th EditionISBN: 9780321979421Margaret L. Lial, Nathan P. Ritchey, Raymond N. Greenwell
4,840 solutions
Calculus: Early Transcendentals 8th Edition by James Stewart

Calculus: Early Transcendentals

8th EditionISBN: 9781285741550James Stewart
11,083 solutions
Calculus: Early Transcendentals 9th Edition by Daniel K. Clegg, James Stewart, Saleem Watson

Calculus: Early Transcendentals

9th EditionISBN: 9781337613927 (3 more)Daniel K. Clegg, James Stewart, Saleem Watson
11,050 solutions

More related questions

1/4

1/7