Of course!
My first campaign was a very specific niche (target audience size about 16k) and I spent $50 over several days. My add looked good (I thought) but I got crushed. A CTR near 0.02 and I was paying around $1 a like. It wasn't a competitive niche at all either. I was only paying $0.15 CPM. I was getting tons of impressions, no results.
I decided to give it a go again. Exact same targeting, exact same ad. I spent another $50 and my CTR went from 0.02 to 0.25! Nothing to brag about but way, WAY better. My cost per like went from over $1 to $0.22.
No way this was a coincidence.