Stat 301: Rock weighing plots

In all plots, the black horizontal bars are the true mean weight in that population of rocks. The dots are either the weight of the rock or the average weight in each person's sample. The blue horizontal bars are the average of all samples. Ideally, this is close to the true mean weight.

Rock weights in each group (all 100 rocks, first 50, last 50)
Weights of single "representative" rock, samples are 33% and 13% too high
Average weight of five "representative" rocks, samples are 23% and 12% too high
Average weight of five "grabbed" rocks, samples are 33% too high
Average weight of five rocks chosen by die roll, samples are 3% and 6% too high