# Maths Sample Moments Question

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#1
Prove the following identities:
(m'k = raw sample moment, mk = central sample moment)
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1 month ago
#2
If you have a problem, can you post the full question (is this UG?) and what you've tried/describe what problem you're having.
Last edited by mqb2766; 1 month ago
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#3
(Original post by mqb2766)
If you have a problem, can you post the full question (is this UG?) and what you've tried/describe what problem you're having.
I'm UG, simply I want to try and prove them, but I'm not sure how to.
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1 month ago
#4
(Original post by SuprDooprPoopr)
I'm UG, simply I want to try and prove them, but I'm not sure how to.
So you have notes, what have you covered? Also, can you upload the full question pls?
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#5
(Original post by mqb2766)
So you have notes, what have you covered? Also, can you upload the full question pls?
The full question is just "Prove the following identities" and thats what I need to prove. I know that the raw sample moment is m'k = 1/n (sum Xi^k) and the central sample moment is mk = 1/n (sum (Xi-Xbar)^k). I've seen the identities on the internet but they all just say the answer and I'm not sure how they actually get to that answer.

edit: sorry I don't know how to do symbols of sums etc
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1 month ago
#6
(Original post by SuprDooprPoopr)
The full question is just "Prove the following identities" and thats what I need to prove. I know that the raw sample moment is m'k = 1/n (sum Xi^k) and the central sample moment is mk = 1/n (sum (Xi-Xbar)^k). I've seen the identities on the internet but they all just say the answer and I'm not sure how they actually get to that answer.

edit: sorry I don't know how to do symbols of sums etc
The first two parts are easily available, they were top of the list when I googled (to check) last night. But it's generally good to prove the simpler ones yourself. It's also good to upload a pic of the actual question and any other relevant parts. Can you pls do it.

Have you been tried the first one? It's actually hard not to get it correct. Upload what you've tried?
Last edited by mqb2766; 1 month ago
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#7
(Original post by mqb2766)
The first two parts are easily available, they were top of the list when I googled (to check) last night. But it's generally good to prove the simpler ones yourself. It's also good to upload a pic of the actual question and any other relevant parts. Can you pls do it.

Have you been tried the first one? It's actually hard not to get it correct. Upload what you've tried?
I don’t know what else of the question you want me to upload? That’s the whole question.
This is what I have so far:
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1 month ago
#8
(Original post by SuprDooprPoopr)
I don’t know what else of the question you want me to upload? That’s the whole question.
This is what I have so far:
A picture of the question pls.
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1 month ago
#9
(Original post by SuprDooprPoopr)
I don’t know what else of the question you want me to upload? That’s the whole question.
This is what I have so far:
For m1 are you ok with that. What about m2, what problem are you having?
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#10
(Original post by mqb2766)
A picture of the question pls.
Surely you're trolling?
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1 month ago
#11
(Original post by SuprDooprPoopr)
Surely you're trolling?
No. It helps to see the question and how things are defined.
However it also seems to say this is your homework, so I guess you should do it.
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#12
(Original post by mqb2766)
No. It helps to see the question and how things are defined.
However it also seems to say this is your homework, so I guess you should do it.
Obviously, but I want some help, as you should get help when you are struggling! You're clearly not going to help me, if your next message isn't helpful I'm not gonna bother.
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1 month ago
#13
(Original post by SuprDooprPoopr)
Obviously, but I want some help, as you should get help when you are struggling! You're clearly not going to help me, if your next message isn't helpful I'm not gonna bother.
See the questions in #9.

In your OP there is no indication of what you'd done/what problems you're actually having. Both things will get more informative responses quicker. A picture of the actual question helps as sometimes people don't give a full description. See the sticky at the top of the forum.
https://www.thestudentroom.co.uk/sho....php?t=4919248
Last edited by mqb2766; 1 month ago
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#14
(Original post by mqb2766)
See the questions in #9.

In your OP there is no indication of what you'd done/what problems you're actually having. Both things will get more informative responses quicker. A picture of the actual question helps as sometimes people don't give a full description. See the sticky at the top of the forum.
https://www.thestudentroom.co.uk/sho....php?t=4919248
who?
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1 month ago
#15
(Original post by SuprDooprPoopr)
Obviously, but I want some help, as you should get help when you are struggling! You're clearly not going to help me, if your next message isn't helpful I'm not gonna bother.
Some brief hints:

Rather than expanding out (which is going to make things more complicated), you want to replace by (so things get *less* complicated).

As far as a summation goes, is a constant (it doesn't depend on i), so, for example, .

Don't write " because ..." unless the "..." is actually going to explain/prove why the statement is true. You've simply put down some definitions and substituted them into the problem. It's not clear if you think erroneously that this constitutes a proof, or you're just laying out some basic facts, but either way, that "because" is not justified and is confusing.

For these problems, you're actually going to be better off starting from the definitions of [tex]m_1', m_2', m_3'[/tex and trying to get to the desired expressions, rather writing down both the starting point and ending point and trying to show they're equal (as you appear to be attempting).
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