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Vlad [161]
3 years ago
14

If​ Tucson's average rainfall is

Mathematics
1 answer:
S_A_V [24]3 years ago
4 0
You think I know right? yeah so no way boy I'm so sorry not my intencion
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Let X and Y be discrete random variables. Let E[X] and var[X] be the expected value and variance, respectively, of a random vari
Ulleksa [173]

Answer:

(a)E[X+Y]=E[X]+E[Y]

(b)Var(X+Y)=Var(X)+Var(Y)

Step-by-step explanation:

Let X and Y be discrete random variables and E(X) and Var(X) are the Expected Values and Variance of X respectively.

(a)We want to show that E[X + Y ] = E[X] + E[Y ].

When we have two random variables instead of one, we consider their joint distribution function.

For a function f(X,Y) of discrete variables X and Y, we can define

E[f(X,Y)]=\sum_{x,y}f(x,y)\cdot P(X=x, Y=y).

Since f(X,Y)=X+Y

E[X+Y]=\sum_{x,y}(x+y)P(X=x,Y=y)\\=\sum_{x,y}xP(X=x,Y=y)+\sum_{x,y}yP(X=x,Y=y).

Let us look at the first of these sums.

\sum_{x,y}xP(X=x,Y=y)\\=\sum_{x}x\sum_{y}P(X=x,Y=y)\\\text{Taking Marginal distribution of x}\\=\sum_{x}xP(X=x)=E[X].

Similarly,

\sum_{x,y}yP(X=x,Y=y)\\=\sum_{y}y\sum_{x}P(X=x,Y=y)\\\text{Taking Marginal distribution of y}\\=\sum_{y}yP(Y=y)=E[Y].

Combining these two gives the formula:

\sum_{x,y}xP(X=x,Y=y)+\sum_{x,y}yP(X=x,Y=y) =E(X)+E(Y)

Therefore:

E[X+Y]=E[X]+E[Y] \text{  as required.}

(b)We  want to show that if X and Y are independent random variables, then:

Var(X+Y)=Var(X)+Var(Y)

By definition of Variance, we have that:

Var(X+Y)=E(X+Y-E[X+Y]^2)

=E[(X-\mu_X  +Y- \mu_Y)^2]\\=E[(X-\mu_X)^2  +(Y- \mu_Y)^2+2(X-\mu_X)(Y- \mu_Y)]\\$Since we have shown that expectation is linear$\\=E(X-\mu_X)^2  +E(Y- \mu_Y)^2+2E(X-\mu_X)(Y- \mu_Y)]\\=E[(X-E(X)]^2  +E[Y- E(Y)]^2+2Cov (X,Y)

Since X and Y are independent, Cov(X,Y)=0

=Var(X)+Var(Y)

Therefore as required:

Var(X+Y)=Var(X)+Var(Y)

7 0
3 years ago
Hao bought a 16-pound bag of dog food. If his dog eats pound of food every day, for how many days will the bag of dog food last?
densk [106]

Answer:

uh 1 pound per day 16 pounds so 16 days, i guess

Step-by-step explanation:

3 0
2 years ago
Read 2 more answers
No clue how to do this someone please help
Free_Kalibri [48]

Answer:

I recommend trying this it is real tutors that explain to you on how to do it it's free

7 0
3 years ago
Can anyone help me? The top is geometry and the bottom is algebra...
umka21 [38]

Answer:

<u>Geometry</u>

AC equals 13x + 7

<u>Algebra</u>

1. x = -16

2. x = 2

3. 2x^2 - 5x -7

4. (2x + 1)(x - 5)

Step-by-step explanation:

6 0
3 years ago
This system of equations has an infinite number of solutions. Define the solutions algebraically, and allow z to represent all r
Soloha48 [4]

Answer:

x = 12z + 1  and y = 10z - 1

Step-by-step explanation:

To solve the system of equations, we can use the substitution method

If we call

3x - 4y + 4z = 7 I

x - y - 2z = 2 II

2x - 3y + 6z = 5 III

Clearing II  x = 2 + y + 2z

Now, replacing II in III

2(2 + y + 2z) - 3y +6z = 5

4 + 2y + 4z - 3y + 6z = 5

10z - y = 1 from here y = 10z - 1

Finally, replacing y in I

3x - 4(10z - 1) + 4z = 7

3x -40z + 4 + 4z = 7

3x - 36z = 3

3x = 36z + 3

x = 12z + 1

Done

7 0
3 years ago
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