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# Standard Deviation?

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1. How do you work out the standard deviation from these three pieces of data?

Replicate 1: 725 Replicate 2: 699 Replicate 3: 824
2. Here's how they found the first one, now have a go yourself at the missing one

Although this is not a maths paper so I don't know what they're expecting you to do - do you have a cassio with stats mode? You can work it out very quickly on there.
3. I'm going to use the example for the first row since the numbers are all there.

1) Calculate the mean of the values which is 328.0

2) subtract the mean from each individual data set.
So 324-328.0=-4
362-328.0= 34
298-328.0= -30

3) square each of the values to get rid of any negatives
So -4^2 is 16
34^2 is 1156
-30^2 is 900

4) total up the squared numbers
This was 2072

5) you then divide the total of numbers by n-1 (where n is the number of values)
2072/2= 1036

6) to get to the final value, simply square root the answer above which equals to 32.2 when rounded to one decimal place.

This conforms to the standard deviation formula the user above posted.

Try this for the second row now.
4. (Original post by QPRTeags)
Here's how they found the first one, now have a go yourself at the missing one

Although this is not a maths paper so I don't know what they're expecting you to do - do you have a cassio with stats mode? You can work it out very quickly on there.
Thanks, that was very helpful. I got 66.523, which I think is correct. This is from a practice Biology paper to prepare me for my exam next Wednesday. Thanks to you I may just pass. Or, at least get a question like this correct in my exam!
5. (Original post by aamirac)
I'm going to use the example for the first row since the numbers are all there.

1) Calculate the mean of the values which is 328.0

2) subtract the mean from each individual data set.
So 324-328.0=-4
362-328.0= 34
298-328.0= -30

3) square each of the values to get rid of any negatives
So -4^2 is 16
34^2 is 1156
-30^2 is 900

4) total up the squared numbers
This was 2072

5) you then divide the total of numbers by n-1 (where n is the number of values)
2072/2= 1036

6) to get to the final value, simply square root the answer above which equals to 32.2 when rounded to one decimal place.

This conforms to the standard deviation formula the user above posted.

Try this for the second row now.
6. (Original post by doitforyou)
Thanks, that was very helpful. I got 66.523, which I think is correct. This is from a practice Biology paper to prepare me for my exam next Wednesday. Thanks to you I may just pass. Or, at least get a question like this correct in my exam!
Yes, 66.5 is correct, well done!

No problem, good luck in the exam!

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