I finished my third hat using the same pattern. The pattern was written for hand spun wool.
I thought by substituting it with an Aran store bought factory made yarn would be alright. That yarn is said to be knitted on #9 needles. The first hat I made using that pattern and #9 with Noro Kochoran is large. It is also loose. My husband says it gives it a classy look. It is supposed to be more of a tight winter hat but it is baggy and has a bit of a shape to it. It is not supposed to look that way.
For hat #2 with same pattern and another Aran yarn by Noro (Iro) I downsized to #8 needles. I thought the length was okay but when it was done, it fit like a tight winter hat and my earlobes are exposed.
For hat #3 I used a worsted weight handpainted wool yarn by a cottage industry from Pennsylvania. I also knit in two strands, the second being a mohair boucle with #8 needles. The result is a tightly knit winter hat that is tight to my head and does cover my ears. This is the tightest hat so far.
I have come to the conclusion that this is a gauge issue.
I am a non-conformist and resent being told in a pattern which exact yarn to use. I want to pick the yarn I want and then find a look I like and have it turn out right. I've been reading "Knitting Rules" by Stephanie Pearl-McPhee. The chapter on gauge has been eye-opening. Now I just need to be sure to use a pattern that explains the gauge and to knit a swatch and figure it out from there.
This is on my mind as I contemplate jumping in to knit my first sweater. I have all the yarn ready to go (purchased at the New York Sheep and Wool Festival a couple of weeks ago).