Why must experiments be repeated many times

Experiments must  be repeated to provide evidence of a hypothesis. 

When you have an hypothesis about something, you run an experiment to see if your predictions are true. As science becomes more evolved and sophisticated, we learn more about the world around. Thus, gaining more fact about the world around us. We will then re-try an experiment with our new found knowledge and see if the experiment checks out still.

Since a female is both xx chromosome and the male passes down the x chromosome, than the offspring would be female since a female is xx.

If you eat to much it could kill you.