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# Standard deviation- can you get standard deviation without repeating results watch

1. so for example instead of using a mean you just use the one value you recorded... cant do standard deviation then? and if so you cant do error bars?
2. Standard deviation is a measure of the spread of a data set. So with only a single result you can't have a spread if that makes sense?
3. (Original post by Bruhh)
Standard deviation is a measure of the spread of a data set. So with only a single result you can't have a spread if that makes sense?
yes, thank u sir
4. (Original post by Bruhh)
Standard deviation is a measure of the spread of a data set. So with only a single result you can't have a spread if that makes sense?
you know error bars on line graphs? they just make it look really scruff? plus how can you tell which error bar is overlapping which?
5. Well you can tell if they overlap by looking at the upper value of one set of bars and the lower value of another and seeing if the lower value of one is less than the upper value of the other. If it is then they must overlap.

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6. (Original post by Bruhh)
Well you can tell if they overlap by looking at the upper value of one set of bars and the lower value of another and seeing if the lower value of one is less than the upper value of the other. If it is then they must overlap.

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u at uni
7. (Original post by neverbeejail)
u at uni
I'm in year 13 currently

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8. (Original post by Bruhh)
Standard deviation is a measure of the spread of a data set. So with only a single result you can't have a spread if that makes sense?
That's what I said (in another thread of his.) ;p

But kudos to your next post.
9. (Original post by neverbeejail)
so for example instead of using a mean you just use the one value you recorded... cant do standard deviation then? and if so you cant do error bars?
It depends:

Standard deviation of a constant is 0.

Estimated standard deviation of one sample is undefined.

So if your population size is 1, then your s.d is 0.
10. Correct me if I'm wrong, but I think the error bars you're referring to are represented by standard error, not standard deviation.
11. (Original post by aymanzayedmannan)
Correct me if I'm wrong, but I think the error bars you're referring to are represented by standard error, not standard deviation.
how do u calculate standard error? i just had to make up results to get the average then in excel used the standard deviation of each independent variable respectively to make error bars for 95% confidence intervals

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Updated: November 7, 2015
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