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# Standard Deviation watch

1. How do I do standard deviation and mean when only given a large bunch of big numbers? (Please explain in an easy to understand way, this was a question that I completely failed in my test)
2. Omg I'm doing Statistics.

I'm just learning myself but standard deviation is the amount between each score or value.

Standard dev is the square root of the variance. You have to do variance 1st.

I don't know how you got to standard deviation and don't know how to do mean. But mean is the average. Look up how to do average, then do variance. Then tap square root on your calculator...
3. Hi, Given a large bunch of numbers you will need to calculate the mean. That is all the numbers added together divided by the amount of numbers there are. so if u have 78 numbers for example, your mean would be all the numbers added together divided by 78.

Standard deviation is best described with an example. Say we have the numbers:

2 4 5 6 8 9 10 and 12 to find the variance is the mean of the squares, minus the squares of the mean.

The mean is (2+4+5+6+8+9+10+12)/8 = 7 squaring this is 49. This is the square of the mean

the squares of 2 4 5 6 8 9 10 and 12 would be 4 16 25 36 64 81 100 and 144. thats eight numbers so the mean of this set of numbers is (4+16+25+36+64+81+100+144)/8= 58.75 So the mean of the squares is 58.75

SO the mean of the squares minus the square of the mean is 58.75 - 49 = 9.75 this is the variance

The standard deviation is just the square root of this which is 3.12 (2dp)

(Disclaimer. If you are doing further maths there will be a slightly different method if you are sampling)
4. (Original post by TheEngineer12345)
Hi, Given a large bunch of numbers you will need to calculate the mean. That is all the numbers added together divided by the amount of numbers there are. so if u have 78 numbers for example, your mean would be all the numbers added together divided by 78.

Standard deviation is best described with an example. Say we have the numbers:

2 4 5 6 8 9 10 and 12 to find the variance is the mean of the squares, minus the squares of the mean.

The mean is (2+4+5+6+8+9+10+12)/8 = 7 squaring this is 49. This is the square of the mean

the squares of 2 4 5 6 8 9 10 and 12 would be 4 16 25 36 64 81 100 and 144. thats eight numbers so the mean of this set of numbers is (4+16+25+36+64+81+100+144)/8= 58.75 So the mean of the squares is 58.75

SO the mean of the squares minus the square of the mean is 58.75 - 49 = 9.75 this is the variance

The standard deviation is just the square root of this which is 3.12 (2dp)

(Disclaimer. If you are doing further maths there will be a slightly different method if you are sampling)
Thanks this is a great explanation

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Updated: October 11, 2017
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