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## ← Generalize CI - Intro to Inferential Statistics

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Showing Revision 5 created 05/25/2016 by Udacity Robot.

1. All right, so let's look at the first one. We have our sample mean, x bar minus
2. the z score times the standard deviation meaning we have this number of standard
3. deviations less than the mean. And that's what we did with z here being 1.96,
4. since this is 95%. And then over here on the other side, we have our sample mean
5. plus z amounts of standard deviations or standard errors. So this is what we did
6. to find the confidence interval. However we did not subtract Z standard
7. deviations from the population mean. Remember the original population mean was
8. point zero seven, seven, If we did that then we would get a confidence interval
9. for the original population mean. And that's not what we're interested in. This
10. third one, we have our sample mean, minus and instead of Z we have the actual Z
11. value, 1.96 times the standard error. So we have 1.96 standard errors less than
12. this sample mean. So that is what we get. And same with over here we have 1.96
13. standard error plus the sample mean. And this one doesn't really make sense
14. because we can't just subtract the number of standard deviations, we need to
15. multiply this number of standard deviations by what the standard deviation
16. actually is. To find the distance away from the sample mean we need to go.
17. Hopefully that makes sense. Great job.