standard deviation (2 Viewers)

[dzth]

does anyone know how to do standard deviation without a casio calculator?
i have a sharp calculator and it doesnt have the MODE SD function on it..

it's a sharp el-531VH if i remember correctly..
or is there a manual method of doing standard deviation?
please teach me.. thank you!

 

[watatank]

well the formula is √ { [∑(y-y')²]/(n-1)}

where y are the elements
y' is the mean
n= number of elements

manual method:

i'll use an example...

example: find mean and s.d. of 2, 3, 6, 10

mean = (2+3+6+9)/4 = 5

s.d.

calculate ∑(y-y')²
= (2-5)² + (3-5)² + (6-5)² + (9-5)²
= 9 + 4 + 1 + 16
= 30

divide by (n-1) in this case its (4-1) = 3
so 30/3 = 10

now you've got the variance. take square root of all that and you've got the standard deviation.