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# S1 Perplexities watch

1. n=49, sum of (x-200)=245, sum of ((x-200)^2)=9849

Find the mean and standard deviation. Here's what I have so far.

(sum of x-200)+(200*49)=245 +(200*49)
sum of x= 10045
mean of x=205.
How on earth do I go about finding the standard deviation???
2. sqrt(9849/49 - (245/49)^2)

The 200 simply codes the data but won't affect the standard deviation.
3. (Original post by sciortino)
sqrt(9849/49 - (245/49)^2)

The 200 simply codes the data but won't affect the standard deviation.
oh okay, so instead of trying to find x itself, i just use (x-200) as my x and (x-200)^2 as my x^2, if you get what I mean??
4. Yes, because you want the standard deviation and the additive coding won't affect the answer.
If you sought the mean you would need to decode by adding back the 200

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