
Sample Variance
I'm looking at this online text on statistics, and reached Figure 222 on this page. I don't understand what this chart is supposed to represent. When I click "take sample" with sample size 5, taking 1 sample from 100 bins, I get values like 400. But looking at the population, none of the numbers in the population are over 50. So what does a value of 400 represent? The sum of the five samples doesn't even reach 400 in a bestcase scenario.
Also, what does "100 bins" mean? The population doesn't have 100 members. Are some of the members repeated in the 100 bins?
I guess I just generally don't understand any of the meaning of this chart.

Re: Sample Variance
Further question: Standard error is a property of a random variable, right? So how is there a standard error of, say, a sample percentage? I have a guess about the answer, but I want to confirm it. Is it that we treat each possible sample percentage as a value of a random variable. Then the standard error, speaking precisely, is really the standard error of this random variable?