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anonymous
 one year ago
What is the standard deviation of the following data? If necessary, round your answer to two decimal places.
12, 13, 8, 13, 9, 11, 12, 9, 1
anonymous
 one year ago
What is the standard deviation of the following data? If necessary, round your answer to two decimal places. 12, 13, 8, 13, 9, 11, 12, 9, 1

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jtvatsim
 one year ago
Best ResponseYou've already chosen the best response.2I don't think @heretohelpalways that we want the mean absolute deviation for this problem. We need the standard deviation.

jtvatsim
 one year ago
Best ResponseYou've already chosen the best response.2The steps to do this are: 1. Find the mean of the data. (Find the average) 2. Then find subtract each data point from the mean and square the result. 3. Find the mean of the "square differences" we found in step 2. 4. Take the square root of Step 3 and we are done. This is easier to see in a table. Which I will show below.

jtvatsim
 one year ago
Best ResponseYou've already chosen the best response.2Here's the start of my table.

jtvatsim
 one year ago
Best ResponseYou've already chosen the best response.2Let's go ahead and do step 1. What is the mean of the data? To do this, just add up all the data and divided my how many we have.

jtvatsim
 one year ago
Best ResponseYou've already chosen the best response.212 + 13 + 8 + 13 + 9 + 11 + 12 + 9 + 1 = 88 Then, divide this by 9 (that's how many we have), this gives us 88/9 = 9.8. You beat me! Good! :D

jtvatsim
 one year ago
Best ResponseYou've already chosen the best response.2Now, for the annoying part... we have to subtract the mean from each of our data points. So, for example, we do 12  9.8 = 2.2. Then we repeat this for all the other points... BORING! But, not that hard. :)

jtvatsim
 one year ago
Best ResponseYou've already chosen the best response.2When you are done, you will get something like this (I'm cheating since I have a computer that does this for me...)

jtvatsim
 one year ago
Best ResponseYou've already chosen the best response.2Does that make sense so far?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Yep! got it so far, thanks

jtvatsim
 one year ago
Best ResponseYou've already chosen the best response.2Great! Now, for the second part of Step 2. We need to "square" (multiply the number by itself) each of the differences we just found. What am I trying to say? For example, The first difference was 2.2. So find 2.2^2 = 2.2 * 2.2 = 4.84. And do this for each of the differences... BORING AGAIN! But not hard.

jtvatsim
 one year ago
Best ResponseYou've already chosen the best response.2You should get something that looks like this

jtvatsim
 one year ago
Best ResponseYou've already chosen the best response.2Phew! Almost done! Now, we find the mean (average) of these crazy squared numbers. Add them up, divide by how many (9) and we get: 12.6 about.

jtvatsim
 one year ago
Best ResponseYou've already chosen the best response.2This number we just found is called the "variance" of the data. The standard deviation is the square root of this number. So just find sqrt(12.6) = 3.6 and we are done.

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Got it! Thank you so much, that was very well explained!

jtvatsim
 one year ago
Best ResponseYou've already chosen the best response.2Glad to help! No point to make it harder than it already is! :) Good luck!
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