My very first socks were made of 8 ply yarn, just for lounging around at home--and for instant gratification. I've noticed as I've been wearing and washing them that the tension is too loose. When I went back to my book I couldn't remember which pattern I'd used. So, I decided to follow the number one rule of knitting and do a tension square--or a tension cuff in this case.
I also re-read the relevant section in my "Getting Started Knitting Socks" book and realised that the sizes there were given according to US shoe sizes, not Australian. That should have been obvious, but I guess at the time I was so overwhelmed by the excitement of knitting real live socks on double pointed needles that I missed the point. I decided on a firmer tension and larger size. And I decided to keep a record of what I make so next time I won't be so confused.