find the standard deviation of 18,19,20,21,22

Question

cggurumanjunath · Answer

https://in.answers.yahoo.com/question/index?qid=20080620134914AAB7FDj

the_fizicx99 · Answer

1. Find the mean:

$\ \dfrac{18 + 19 + 20 + 21 + 22}{5} $

Mean = 20

2. subtract the original value with the mean,

18 - 20 = -2
19 - 20 = -1
20 - 20 = 0
21 - 20 = 1
22 - 20 = 2

Now square that, 

$\ -2^2 = 4 $ 

$\ -1^2 = 1$

$\ 0^2 = 0$

$\ 1^2 = 1$

$\ 2^2 = 4$

Now divide by add them up and divide by 5, $\ \dfrac{ 4 + 1 + 0 + 1 +4}{5} = \dfrac{10}{5} = 2$

$\sigma = \sqrt{2} = 1.41 $

the_fizicx99 · Answer

The original formula is:

$$\sigma =\sqrt{\Sigma\dfrac{(x - mean)^2}{n}}$$

kc_kennylau · Answer

Mean = Sum / number
Variance = Mean of distances to mean squared
S.D. = square root of variance