## ← Z-Score - Intro to Inferential Statistics

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Showing Revision 5 created 05/24/2016 by Udacity Robot.

1. So we have to find the mean and standard deviation of the sampling
2. distribution. Sorry I'm making you calculate this again even though you did it
3. in the previous lesson. I just want to make sure that you continue to get
4. enough practice doing this. So for the sampling distribution, where we take all
5. samples of size 20, because in this case our sample consisted of 20 students.
6. We have that the mean is the same as the population mean, and the standard
7. error, which is the standard deviation of the sampling distribution, is the
8. population standard deviation, divided by the square root of the sample size.
9. So this is about 0.14. So then this means that this sample mean has a z score
10. equal to 7.13 minus the mean 7.5 divided by 0.14. If you put the more exact
11. values into your calculator, then you'll get a more precise z score rather than
12. using the rounded standard error. So we get about negative 2.59. If we look at
13. the distribution of sample means and here is 7.5 the population mean and the
14. mean of sample means negative 2.59 is way over here, so what does this mean.