Sample Size
Sample size is the number of times you repeat a test to make sure your results are real.
Think of it this way
Taste one chip from a bag to judge the whole bag. Then taste ten chips. Ten gives you a better picture. More tastes means a better judgment.
Explaining sample size by grade level
If you roll one die just once, you can not tell which number comes up most. Roll it thirty times and you start to see a pattern. More rolls give you a better picture. A few tries can trick you, but many tries show what is true.