# S1 Standard Deviation problem

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#1
I'm currently stuck on question iv. I've worked out that the mean is 205 but I'm having trouble applying it to work out the standard deviation.

I've decoded x^2 as 9849 + 400 as it's 200 x 2. So that is 10,249. But I'm confused as to what to do to continue.

How do I work out the standard deviation?

Thank you.

0
6 years ago
#2
(Original post by Peppercrunch)
I'm currently stuck on question iv. I've worked out that the mean is 205 but I'm having trouble applying it to work out the standard deviation.
A coding of X-200 won't effect the standard deviation, so you can work with the sigma (x-200) and sigma (x-200)^2 directly, without decoding them.
2
6 years ago
#3
Correction
0
6 years ago
#4
(9849 + 200squared) - (mean) / 49 = variance

Its the same method as calculating the mean I think , but you square 200 this time, and subtract the mean in the numerator
1
6 years ago
#5
Not sure, check the mark scheme...
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