For my personal teaching lesson, I chose to introduce the concept of a random sample and why it provides a good method of estimating population values.
For the activity students are given a population of Jellyblubbers, a recently discovered marine species. They are tasked with finding an estimate to measure the average length of a typical Jellyblubber. They first sample 10 Jellyblubbers by choice and then repeat the selection process by randomly choosing Jellyblubbers. In the end, they will find that the random sample better captures the true average length of the Jellyblubber population.