Question

how do you find the standard deviation ?

Answer 1

ideally with a calculator since doing it by hand takes a while

Answer 2

what kind of calculator do you have

Answer 3

im using the calculator on my phone cause i don't have one, and im kinda stuck on this question now.

Answer 4

yuck, don't use your phone

Answer 5

use wolfram alpha if you don't have something like a TI83

Answer 6

what is your data set?

Answer 7

109372, 176927, 245477, 203974, 279978

i know the mean, and thats 203145.6 but now im stuck and i need the standard deviation, and i will also need to get both the mean and the standard deviation for another set of numbers.

Answer 8

I used wolfram alpha to get this

http://www.wolframalpha.com/input/?i=standard+deviation+109372%2C+176927%2C+245477%2C+203974%2C+279978

Answer 9

so it is roughly 65530.

Answer 10

but, this is what my assignment states :

If you used your calculator's built-in functions to find the mean and the standard deviation, then you will need to say what brand and model of calculator you were using, and what steps and keys you used to find the mean and the standard deviation. Note: If your calculator shows both a sample standard deviation and a population standard deviation, make sure you use the population standard deviation for your answer.

so i dont know if i can get any points without explaining.

Answer 11

ok, then you have to stick with the basic functions of a calculator

Answer 12

ok so you managed to find the mean right?

Answer 13

ohmygosh i dont understand how to explain how i got it ... i typed it in google and got the same answer as you.


yes, the mean is 203145.6

Answer 14

ok you would then subtract the mean from data value

Answer 15

data value meaning everything added up correct?

Answer 16

from each data value*

Answer 17

sorry mistyped

Answer 18

oh, okay

Answer 19

if you have n data values, you'll have n differences

Answer 20

i guess i dont understand now,

Answer 21

the data values are

109372, 176927, 245477, 203974, 279978

Answer 22

the mean is 203145.6

Answer 23

subtract the mean from each data value to get


109372-203145.6 = -93773.6
176927-203145.6 = -26218.6
245477-203145.6 = 42331.4
203974-203145.6 = 828.4
279978-203145.6 = 76832.4


So the differences are: -93773.6, -26218.6, 42331.4, 828.4, 76832.4

Answer 24

you then square each difference, then add up the squares

then you divide by 5 (since there are 5 data values)

finally you take the square root of that

Answer 25

okay, thats what i thought you meant but i wasnt completely sure, the negative numbers confused me. i thought that wouldnt work out.

so now i take √-93773.6 ? same with all the others?

Answer 26

no square (not square root)

Answer 27

ohhh, i have no idea how to square the number ?

Answer 28

ex: 3^2 = 3*3 = 9

Answer 29

soo, -93773.6 ^ 2 ?

im trying, but i really have no idea how to do these, so im slowly learning,

Answer 30

yeah but you need to use parenthesis

Answer 31

because you need to include the negative as well

Answer 32

oh, of course.
so. let me try this, (-93773.6) ^ 2 = 8793488056.96 (that seems bad)
but if i do that, then square it which means multiply by 3 so 8793488056.96 * 3 = 26380464170.88

what is going on with my numbers!?

Answer 33

why are you multiplying by 3?

Answer 34

(-93773.6) ^ 2 = 8793488056.96 is correct (roughly)

Answer 35

i dont know, that was part of your example. lol. well that was embarrassing.

Answer 36

oh I was just showing you what I meant when I said square it

Answer 37

okay, so what do i do after we have that number then ?

Answer 38

let's finish up squaring each value

Answer 39

(-93773.6)^2 = 8793488056.96
(-26218.6)^2 = 687414985.96
(42331.4)^2 = 1791947425.96
(828.4)^2 = 686246.56
(76832.4)^2 = 5903217689.76

Answer 40

Now add up each square:


8793488056.96+687414985.96+1791947425.96+686246.56+5903217689.76 = 17176754405.2


After this, you divide that sum by 5 (there are 5 data values originally)


17176754405.2/5 = 3,435,350,881.04

finally, you take the square root of this result to get the population standard deviation


sqrt(3435350881.04) = 58,611.8663842059

Answer 41

holy crap and thats it, those are all steps?

Answer 42

yeah I told you it's a lot...now imagine having to this with 10, 20, or 30 data values...not fun at all

Answer 43

i just dont wanna do all this none sense again.

but seriously, thank you for explaining that, cause i could look up the answer from multiple sites just couldnt figure out how they got it.

Answer 44

you're welcome