Thank you all for your interest and comments.
In following the tree, I found the the Alice Crompton I was following, after her marriage to John Waterhouse, the only Alice Crompton I could find, with a father of James, was James Crompton, born about 1800 in Lancashire, and married to Martha Simister..
I will admit freely, that at the time, I did not notice that Alice's father was a hatter

I found a baptism for Alice in Oldham, and her father James was a spinner. It was only when I was doing more checking that I noticed that the marriage register had James as a hatter.
That is why I asked the question, as I was not sure about how different the occupations were.