## ← Z-Table - Intro to Descriptive Statistics

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

1. Remember I said earlier that if we have the equation of the probability density
2. function we can use calculus to find the area under the curve between any two
3. values or between negative infinity in any value. Mathematicians have put these
4. values in a table. Here is the top of this table, it gives you a little diagram
5. saying that when we have the z score, the values in this table tell us the
6. proportion less than that z score, in the standard normal curve. So this table
7. is for the standard normal distribution, and remember that's when the mean is
8. zero and the standard deviation is one. This way, after standardizing any normal
9. distribution. In other words after calculating the z scores for the values that
10. we're interested in, we can use this table to approximate the proportion less
11. than that particular z square. Here, the tenths place runs vertically and the
12. hundredths place runs horizontally. So if we have of a z score of say, negative
13. 2.75. Remember, that would then be less than the mean. Negative 2.7 is here, and
14. 0.05 is here. So if we follow over, these cells meet at .003. So the proportion
15. less than negative 2.75 is .003. Or .3%. So again that's the probability that we
16. get less than negative 2.75. And that's the proportion of objects in the sample
17. that have a score less than negative 2.75. There's a link to the z table that we
18. shared and so use that link when you use the z table which you are going to use
19. in the next quiz.