jungkook123
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calculate the mean and standard deviation of x
n=100
Σ(x-20)=125
Σ(x-20)^2=221
I don't really know where to start with this question, any help will be appreciated
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RDKGames
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(Original post by jungkook123)
calculate the mean and standard deviation of x
n=100
Σ(x-20)=125
Σ(x-20)^2=221
I don't really know where to start with this question, any help will be appreciated
Do you know what the notation means? Because if you don't, it would be a good start to look it up.

Then, do you know how the mean is calculated?
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jungkook123
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(Original post by RDKGames)
Do you know what the notation means? Because if you don't, it would be a good start to look it up.

Then, do you know how the mean is calculated?
no, I don't, I'll go search it up
I'm not really sure how to calculate mean from this kind of equation?
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RDKGames
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(Original post by jungkook123)
no, I don't, I'll go search it up
I'm not really sure how to calculate mean from this kind of equation?
\displaystyle \sum (x-20) means that every single sample point x (all 100 of them) had 20 subtracted from them, and them they were added up. The result is 125.

So if you find the mean of this 'coded' data (i.e. data that had 20 subtracted from each sample point), then you can think about what the mean of the original data must be.

In other words, how does subtracting 20 from each sample point affect the new mean compared to the original one?
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jungkook123
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(Original post by RDKGames)
\displaystyle \sum (x-20) means that every single sample point x (all 100 of them) had 20 subtracted from them, and them they were added up. The result is 125.

So if you find the mean of this 'coded' data (i.e. data that had 20 subtracted from each sample point), then you can think about what the mean of the original data must be.

In other words, how does subtracting 20 from each sample point affect the new mean compared to the original one?
so do you rearrange to make x the subject?
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RDKGames
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(Original post by jungkook123)
so do you rearrange to make x the subject?
No. You need to use knowledge of coded data.

If you are doing Edexcel, look at Page 33 of the Stat & Mech Year 1 textbook.
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jungkook123
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(Original post by RDKGames)
No. You need to use knowledge of coded data.

If you are doing Edexcel, look at Page 33 of the Stat & Mech Year 1 textbook.
im so confused, the general formula, y=x-a/b is different to the question?
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RDKGames
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(Original post by jungkook123)
im so confused, the general formula, y=x-a/b is different to the question?
Not really.

In this particular question you have the case a=20 and b=1.
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