To create this hat, I used both crochet and knitting. It was a spontaneous creation that I designed on the fly, without any specific plan. I didn't use, or write down, a pattern; the entire design was done in freeform.
The hat began its life as a little triangle sample I knitted while practicing my knitted decreases. I can't stand the idea of wasting anything, not even such a tiny little piece of knitting as that one was. So, I decided that the triangle would become the center for my hat.
Crochet and knitting are two different techniques. To my way of thinking, both techniques have distinct advantages, although everybody's opinion will differ about which technique is better for accomplishing any given goal. At the time I was creating this hat, I was a whiz at crochet, and not as proficient at knitting. So I decided that the rest of the top of the hat would be a crocheted circle, and I set to work on it.
When I got to the sides of the hat, I decided that it would have to be knitted. The thing I love best about knitting is its resilience and stretchiness. Crochet stretches too, but it doesn't behave in quite the same way knitting does. I thought that knitted sides would be just what this hat needed.
I think this design utilizes both knitting and crocheting to best advantage. If you're interested in making freeform projects, I invite you to give this type of combination a try; you'll be amazed at how much more versatile it allows you to be with your work.
Another idea for combining crochet and knitting: knit the ribbing and cuffs of a sweater, then crochet the sweater body.