## ← Keyboards - SD of Differences - Intro to Inferential Statistics

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Showing Revision 9 created 05/24/2016 by Udacity Robot.

1. Let's put D as the header in this column. D for difference. If you figured this
2. out yourself, great job. We'll put equals A2 minus B2. And there we have our
3. difference. Then we'll copy this cell, 'cuz we'll copy the formula. Go to cell
4. C26. Highlight the whole column C, and then paste. And we get all our
5. differences. Let's calculate the average difference. We get the same thing we
6. got for our point estimate of the differences. Now let's calculate the standard
7. deviation of these. So we have each value, minus the mean. So remember we're
8. subtracting a negative number, and then square it. So these are our squared
9. deviations from the mean. So we'll sum them up and then divide by n minus 1,
10. which is 24. Finally, we'll take the square root. We get about 3.69.