# Thread: How do I get this approximation?

1. ## How do I get this approximation?

I'm struggling to get the approximation

when after N steps in a random walk the mean=N/6 and variance=N/18. I know that as N becomes very large, we can approximate it to a Normal distribution, but my algebra leaves me this

Any ideas?

2. ## Re: How do I get this approximation?

it would be nice to know what that is approximating.

If it's a normal distribution with the given mean and variance then the N in the numerator of the argument to the exponential function should be N/2

3. ## Re: How do I get this approximation?

Apologies.

I'm trying to show that

using the values for the mean=N*<r>=N/6 and variance=N*Var(r)=N/18 that I mentioned above.