Photoshop :: Trying To Apply A Selective Blur

I am trying to apply a selective blur to a photograph. What I am doing is using the Polygonal Lasso and select around my item. Then I try to use the Ctl +I to invert, but when I do that, the image inside the lasso tool looks polorized. What I am trying to get. it using the Gaussian Blur to blur everything in the background and not the item that I have applied the lasso tool to, everything in the lasso should be clear and everything outside (the background) should be blured.

I am getting this tio from a book called "Retouching cookbook for digital photographers" and it is a simple tip, but it is not turning out.