Question

is anyone good with standard deviations?

Answer 1

nice! would you be willing to help me?

Answer 2

what is the best approximation of the standard deviation of the measures -4, -3, 0, 8 and 9?

Answer 3

is that all your problem states?

Answer 4

if so, find the mean and subtract it from all the data points, square and add the results

then divide by how many data points there are (assuming that this is a population), and take the sqrt of that

Answer 5

Thanks for the thorough explanation.. I appreciate it!

Answer 6

your welcome; in formula it reads as:\[\sigma^2=\frac{\sum(x-\mu)^2}{N}\]

Answer 7

where sigma squared is variance; and standard deviation is the squareroot of variance

Answer 8

if you need any help working thru that, just ask :)

Answer 9

yea i might need a little help haha

Answer 10

ok, find the mean for me, simply add up all the values and divide by how many there are

Answer 11

2

Answer 12

subtract 2 from all the points given and list the results then

Answer 13

-6, -5, -2, 6, 7

Answer 14

good, now square all those values and add them up

Answer 15

you get a positive when you square a negative, right?

Answer 16

yes

Answer 17

i got 150

Answer 18

good, thats the top number for our formula; the bottom is just 5 so

150/5 = variance

the square root of variance equals our standard deviation; so what do we get?

Answer 19

30

Answer 20

the denominator is the amount of numbers that we have?

Answer 21

depends, if its a population then yes; if its a sample then its one less

Answer 22

im assuming the data represents a population so divide by the number of data points; 5 in this case

Answer 23

ok.. so the answer would be 30?

Answer 24

30 is our variance value; take the square root of that for the standard deviation

sqrt(30) = what?

Answer 25

i got 5.48

Answer 26

then thats it. Im not sure what you mean by best approx tho; but if you have choices, its bound to be close to that; if not try dividing it by 4 instead of 5

Answer 27

it was a multiple choice and 5 is the closest to it so I believe that 5 is the answer

Answer 28

Thank you soooooo much for the fantastic help =]

Answer 29

youre welcome.

Answer 30

if we divide by 4 I get 6.12 or so; so it all depends on if they are looking for a population or a sample standard deviation

Answer 31

I think it's for a population, but it didn't say anything.. I copied down the exact question, but I think you got it right

Answer 32

good luck ;)

Answer 33

thanks!

Answer 34

There's an online standard deviation calculator which might be used later by the Askee once the concept of standard deviation is learned.

Attached is a .jpg of the "calculator" results if anyone is interested.

http://easycalculation.com/statistics/standard-deviation.php