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S1 Discrete Random Variables watch

1. I'm a tad stuck on this question and was wondering if anyone could help me out with a step by step example? Thankyou!

The random variable T has a mean of 20 and a standard deviation of 5.
It is required to scale T by using the transformation S = 3T + 4
Find E(S) and Var(S)
2. it sounds more like S1 or S2 than C2 ?
3. (Original post by Kaylalou_21)
I'm a tad stuck on this question and was wondering if anyone could help me out with a step by step example? Thankyou!

The random variable T has a mean of 20 and a standard deviation of 5.
It is required to scale T by using the transformation S = 3T + 4
Find E(S) and Var(S)
E(3T +4) = E(3T) + 4 = 3E(T)

Var(3T+4) = Var(3T) = 3^2Var(T) = 9Var(T)

You know E(T) = 20 and Vart(T) = 5^2 = 25.
4. i f Y = 5X - 4

then E(Y) = 5E(X) - 4

& Var(Y) = 25Var(X)
5. Oh, and I'm moving this to maths (and correcting the title to S2, which is what I think you mean).
6. (Original post by the bear)
it sounds more like S1 or S2 than C2 ?
Oops typo, it is S1
7. (Original post by Zacken)
E(3T +4) = E(3T) + 4 = 3E(T)

Var(3T+4) = Var(3T) = 3^2Var(T) = 9Var(T)

You know E(T) = 20 and Vart(T) = 5^2 = 25.
Thankyou, this was really helpful and I apologise I just joined so I'm not quite sure how to navigate this site properly yet haha
8. (Original post by Kaylalou_21)
Thankyou, this was really helpful and I apologise I just joined so I'm not quite sure how to navigate this site properly yet haha
Glad it was helpful, don't worry about it - just remember that in the future, maths questions go in maths study help. :-)

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