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Now I'm going to ask you to consider something which may at first seem a bit odd.
Imagine that I have a box or a bag filled with thousands of marbles (small balls).
Some of the marbles are red. Some are blue.
I want to know the proportion of marbles in the bag which are red.
There are so many marbles in the bag! I don't have time to count all of them.
I decide to reach into the bag (with my eyes closed) and select 20 marbles.
This will be a "random sample" of size 20. I might write n=20 to symbolize this.
Let's say that 12 of the 20 marbles in my sample are red. I might write x=12
So, I picked 20 marbles and 12 were red.
12/20 = .6
So.
I think now about the whole bag, about its "population" of thousands of marbles.
I think about my objective: to know the proportion of marbles in the bag which are red.
Is the answer .6?