Well, no...

Let's use a more realistic analogy. I throw thousands of nickles and dimes at you. You have a filter which has random sized holes in it, all about coin sized, but varied. You can squeeze those holes a little, or relax them a little. If you squeeze them, it becomes more likely that a dime will make it through, if you relax, nickles have a better chance.

This is independent of how many nickles I mix into the dimes. Since only the first one counts, as long as I supply both nickles and dimes, the filter does the choosing.

The enviroment does the choosing, as someone else mentioned a change in ph makes a huge difference. The sperm levels and the egg are minor effects.

So it is the body chemistry of the woman that decides, statistically, if it will be a boy or a girl.