# Talk:Mean squared displacement

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The expanded formula shown on the page should be <x^2> + x0^2 - 2<x>*x0

Not plus.

## MSD main equation units inconsistency

Hi, fellow Wikipedia editors,

I believe the first equation for the MSD is incorrect in the sense that it provides the wrong units as an answer. The units for the MSD should be [L²], whereas the multiplication by (1/T) outside the summation term makes it result on units of [L²/T].

My suggestion is to replace the symbol T which gives the sense of "time" here (and so is described just below the equation), while it actually seems to be playing the role of a "number of discrete samples".

Please take a look at this request, I'm not an Wikipedia editor myself but as an user I struggled with this equation during a code implementation.

Thanks!

Fzigunov (talk) 00:18, 7 August 2016 (UTC)

Good point. I've replaced the definition of T under the equation by "T is the number of timepoints over which one wants to average" (instead of "T is the time..."). Hope that's ok? Qwfp (talk) 12:22, 7 August 2016 (UTC)