## ← st095 18_s_Random selection

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Showing Revision 2 created 02/05/2013 by Cogi-Admin.

1. So, the first one is random. We assign a unique number, 1 to n, to each object.
2. And then, we randomly choose numbers from 1 to n. This results in every object
3. in the population having an equal chance of being selected. The second one's
4. kind of tricky. We don't know for sure if it's random because we don't know if
5. we randomly assigned a unique number. We have to make sure that if we're going
6. to give each object a number, it has to be randomly assigned, and each object
7. has the same chance of getting any number. This one, we took care of that. We
8. randomly assigned a unique number, and then we chose multiples of six. Now, this
9. choosing multiples of six might throw you off a little bit, because that doesn't
10. seem random. But, every object in the population has an equal chance of being a
11. multiple of 6. And finally, this one is also random. This one's actually called
12. stratified sampling, because we divided the population into subpopulations, in
13. this case two. And, every object in the population had an equal chance of being
14. in either one of the subpopulations. And then, random samples were taken from
15. each group, so this is also random. So yay, you're done with Lesson 1. Moving
16. onto the problem set.