# Statistics

#### Roaa_essam12

##### New member
I need help with these questions

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#### Harry_the_cat

##### Elite Member
Where are you stuck? Or do you just want all the answers?

#### Harry_the_cat

##### Elite Member
Seriously? Wouldn't that be cheating? Don't you think that is wrong? No-one here will do that for you. Read the rules of this forum.

#### ISTER_REG

##### Junior Member
I will explain, what you need to know, to solve this.

For the first sheet:
a.) You have a given E[X] = 0.5 and want to find the value of a, use the definition of E[X], which is a sum that is equal to 0.5, e.g. E[X] = -2*p(-2) + ... + 4*p(4) = 0.5
b.) Also similar to a.) use the definition of Var[X] = E[X^2] - E[X]^2
c.) Plug in the terms in the definitions an solve the equations
d.) Rewrite 4X^2 > Y to X > sqrt(Y)*2 --> sqrt(Y)*2 < X, how does one calculate P(X < x) for discrete random variables?

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#### ISTER_REG

##### Junior Member
Now that some time has passed... I would like to share my answers, I would be happy for a confirmation/contradiction First sheet (discrete rand. var. with missing entries in table)
a.) a = 1/4
b.) b = 13/100, c = 6/25
c.) E[Y] = 1, Var[Y] = 320.64
d.) 37/100