# Is it correct to use plus or minus symbol before standard deviation?

I have represented standard deviation as "±SD" before in publications. But I like to have opinions on this. Is it appropriate to use the notation '±' with SD ? Or is it only for Standard error ?

Yes! you can represent standard deviation as "±SD".

For Example:- $\bar x\pm 2\times SD$, it just shows the lower and upper limit for most of individual output $x_i$ of Normal data. ($\mu ~rather~than~ \bar x$)

and, $\bar x\pm 2\times SE~of~mean$, shows lower and upper limit of population mean.

• $\bar{x} \pm 2\mathrm{SD}$ could be an asymptotic 95% prediction interval for a Gaussian random variable (asymptotic because the sample mean, & perhaps the standard deviation, are estimated from the data; so exact prediction intervals are somewhat wider). – Scortchi - Reinstate Monica Apr 21 '15 at 9:46
• Yes @Scortchi! That's why I said most of individual output. – Hemant Rupani Apr 21 '15 at 9:49