Now that you have a sense of how sample size affects your estimate of the "true" mean of a population, consider how the design of your sampling technique might be affected by the population to which you want to extrapolate.
Suppose you want to know the average height of one-year old white pines from the following:
How would sampling design be affected by changing the level to which you want to extrapolate? What factors would need to be considered in designing your sampling methods?
When designing experiments, keep in mind the need for taking random samples that reflect the variability and range of the population under study.