Question

Let X be a continuous random variable with a PDF of the form fX(x)={c(1−x),0,if x∈[0,1],otherwise.

Find the following values.

1. c=

2. P(X=1/2)=

3. P(X∈{1/k:k integer, k≥2})=

4. P(X≤1/2)=

Answer #1

Let X be a continuous random variable with a PDF of the form
fX(x)={c(1−x),0,if x∈[0,1],otherwise.
c=
P(X=1/2)=
P(X∈{1/k:k integer, k≥2})=
P(X≤1/2)=

3. Let X be a continuous random variable with PDF
fX(x) = c / x^1/2, 0 < x < 1.
(a) Find the value of c such that fX(x) is indeed a PDF. Is this
PDF bounded?
(b) Determine and sketch the graph of the CDF of X.
(c) Compute each of the following:
(i) P(X > 0.5).
(ii) P(X = 0).
(ii) The median of X.
(ii) The mean of X.

5. Let X be a continuous random variable with PDF
fX(x)= c(2+x), −2 < x < −1,
c(2−x), 1<x<2,
0, elsewhere
(a) Find the value of c such that fX(x) is indeed a PDF.
(b) Determine the CDF of X and sketch its graph.
(c) Find P(X < 1.5).
(d) Find m = π0.5 of X. Is it unique?

The random variable X has the PDF
fX(x) = { 1/4 -3<=x<=1
{ 0 otherwise
If Y = (X - 2)^2 Find E|Y| Var|Y|

Let X be a random variable with pdf given by fX(x) = Cx2(1−x)1(0
< x < 1), where C > 0 and 1(·) is the indicator
function.
(a) Find the value of the constant C such that fX is a valid
pdf.
(b) Find P(1/2 ≤ X < 1).
(c) Find P(X ≤ 1/2).
(d) Find P(X = 1/2).
(e) Find P(1 ≤ X ≤ 2).
(f) Find EX.

2. Let X be a continuous random variable with pdf given by f(x)
= k 6x − x 2 − 8 2 ≤ x ≤ 4; 0 otherwise.
(a) Find k.
(b) Find P(2.4 < X < 3.1).
(c) Determine the cumulative distribution function.
(d) Find the expected value of X.
(e) Find the variance of X

4. Consider a continuous random variable X which has pdf fX(x) =
1/7, 0 < x < 7.
(a) Find the values of µ and σ^ 2 . (You may recognize the model
above, and if you do, it is OK to simply write down the answers if
you know them.)
(b) A random sample of size n = 28 is taken from the above
distribution. Find, approximately, IP(3.3 ≤ X ≤ 3.51). Hint: use
the CLT.

Let X be a continuous random variable with probability density
function (pdf) ?(?) = ??^3, 0 < ? < 2.
(a) Find the constant c.
(b) Find the cumulative distribution function (CDF) of X.
(c) Find P(X < 0.5), and P(X > 1.0).
(d) Find E(X), Var(X) and E(X5 ).

Let ? be a random variable with a PDF
?(?)= 1/(x+1) for ? ∈ (0, ? − 1). Answer the following
questions
(a) Find the CDF
(b) Show that a random variable ? = ln(? + 1) has uniform ?(0,1)
distribution. Hint: calculate the CDF of ?

Let X and Y be random variables with the joint pdf
fX,Y(x,y) = 6x, 0 ≤ y ≤ 1−x, 0 ≤ x ≤1.
1. Are X and Y independent? Explain with a picture.
2. Find the marginal pdf fX(x).
3. Find P( Y < 1/8 | X = 1/2 )

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