## ← What We Need to Compare the Means - Intro to Descriptive Statistics

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Showing Revision 4 created 05/25/2016 by Udacity Robot.

1. We can easily calculate the probability for discrete samples like this one in a
2. discrete population, but what about in real life, with huge populations? We
3. can't possibly calculate the mean of every possible sample of size n and even if
4. we could, we wouldn't want to. We ended up with 16 samples when we just had a
5. population of size 4. What if we had a population of 350 million? Which is often
6. the case. Well, you've already seen that the distribution of sample means is
7. normal. And we know that the mean of all these sample means is the population
8. mean. Remember, the population mean here was 2.5. And the mean of all possible
9. sample means is also 2.5. So, if we have a random sample and we take the mean of
10. it, how can we know where it falls on this distribution of sample means. We're
11. missing one important thing. Do we need to know the total number in the
12. population? The standard deviation of the distribution of sample means? Which is
13. this here. Or, the total number of possible samples?