Question

Scientists often repeat experiments multiple times. Why is this important

Answer 1

So that they can see if the results are the same, and so that they can ask questions about the experiment and point out problems. Although some variation in results is acceptable, the results from different scientists should be similar- if the results are not similar and consistent then the experiment must be done again.

Answer 2

You need a variable. If something happens once it could just be chance. Like if you got a lottery ticket and won, it would just be chance. Not the thing that happens the most.