Had time to read a couple more pages. 
Straight run is "as hatched" -- unsexed birds.
My first batch of chicks hatched 7 and only got 2 females. If you ordered a couple hundred birds you should be able to expect 50% male and 50% female, but in small batches random chance can tip one way or another.
This!
Vent sexing is never more than about 90% accurate so for every 10 pullets you order you should expect 1 male.
I haven't done it, but I have heard of people who would make a large order of the super cheap "fry pan special" random assorted males and count on getting some mis-sexed females for their layer flock as well as the males for the freezer.

Along those lines, I was wondering would they do that to somebody. Make MOST of the order roos???? They know don't nobody want a buncha roos. Some are cool; but not 7/10. Geeesh. I could see even half; but not most. Really??? Speak to me.
Straight run is "as hatched" -- unsexed birds.
My first batch of chicks hatched 7 and only got 2 females. If you ordered a couple hundred birds you should be able to expect 50% male and 50% female, but in small batches random chance can tip one way or another.
It's also actually very common to receive a mail or two when you order nothing but females.
This!
Vent sexing is never more than about 90% accurate so for every 10 pullets you order you should expect 1 male.

I haven't done it, but I have heard of people who would make a large order of the super cheap "fry pan special" random assorted males and count on getting some mis-sexed females for their layer flock as well as the males for the freezer.