With seeds, you get a 50/50 shot at male or female. IMO, warmer temps during the seedling stage result in higher male ratio, cooler temps result in a higher female ratio.
Now that's anecdotal evidence as observed by me. Take it with a grain of salt
light spectrum and nutrients availibility play an important role too... back in the days i used to start seeds in plagrons grow mix (soil ec: 1,4) and hps light. used to get abour 50/50 males/females. once i started using cocos or seedling soil and metal halide, and feeding the babies with 0,7 ec after the 1st set of leaves, i started getting rather 80/20 or 90/10 females/males. also, it seems that the higher the sativa percentage, the higher the female ratio... with 100% sativas i mostly get 90 - 95% females.