Final answer:
Sandy's experience with different average heights in two random samples exemplifies random sampling variation, which is normal in statistics due to the random nature of sample selection from a population.
Step-by-step explanation:
When Sandy takes two random samples of her classmates and finds that the average heights are different, this is an example of random sampling variation. This occurs because, as she is dealing with a sample of a population rather than the entire population, each sample she takes may yield slightly different results due to the random selection process.
Despite using random sampling methods, such variations are expected and natural, and they are neither indicative of biased sampling, researcher error, nor necessarily sampling error. However, a larger sample size can reduce the chances of these variations affecting the study's conclusions significantly by closely representing the population's characteristics.