np.norm scale parameter should be standard deviation, not variance

[garyzhubc]

Unlike np.random.multivariate_normal where covariance matrix is used as parameter, np.random.normal takes in location and scale, where scale parameter should be set to its standard deviation.

Here is the link https://github.com/wiseodd/wiseodd.github.io/blob/master/_posts/2015-10-09-gibbs-sampling.md