# Thread: Variance and the second moment

1. ## Variance and the second moment

Need some help understanding some basic concepts.

I understand the first moment of a distribution as being a central point about which the distribution balances. Is this a correct understanding?

I cannot visualise any higher moments though, not even the second moment. It seems to be related to variance, though quite why i'm not sure.

I'd really like to be able to visualise these things rather than just accepting them. Any help appreciated.

2. ## Re: Variance and the second moment

Originally Posted by Prometheus
I cannot visualise any higher moments though, not even the second moment. It seems to be related to variance, though quite why i'm not sure.
you could think about it as the average squared distance from the mean. not sure if that helps?

if you're familiar with some linear algebra, you can think about taking the norm (hence, the length) of a random (centered) vector as a way of obtaining the variance.

3. ## Re: Variance and the second moment

Well I think of standard deviation as the average distance from the mean. It's the squared bit of the variance that gets me, it's only done otherwise it would be zero right? But how to visualize the 2nd moment?

I know a tiny bit of linear algebra but not enough to follow you. Do you know any links to videos describing it.

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