yes, what I meant by "it's not calculating the standard deviation" is that it's not the same as calling `np.std` on the dense version of the array. I agree that it's merely a factor of `n_samples ** .5` out. But is there any reason for this? Or is it an error that was never tested? Why didn't the `sparse_centre_data` code use:
```python
X_mean, X_std = csc_mean_variance_axis0(X)
if normalize:
    np.sqrt(X_std, X_std)
```
instead of calling `sparse_std`?