1. An animal clinic kept record of the life spans of certain poodles. The number of years the dogs lived are 8, 10, 12, 15, 17, and 13. What is the standard deviation of the poodle life spans?

Question

1.	An animal clinic kept record of the life spans of certain poodles.  The number of years the dogs lived are 8, 10, 12, 15, 17, and 13.  What is the standard deviation of the poodle life spans?

anonymous · Answer

do you know the standard deviation formula?

anonymous · Answer

it should be around the sqrt(102/10)

anonymous · Answer

whats the formula

anonymous · Answer

phinx828--go back to the other question

yuki · Answer

to find the SD, you need to know the formula

$$\sqrt({1 \over n} \sum {(x*-x_i)^2})$$

anonymous · Answer

sqrt(107/10)*

anonymous · Answer

Here!

anonymous · Answer

thats confusing, i never saw that formula

yuki · Answer

usually the steps are as follows

1), find x* which is the mean
2), list the square of mean deviations 
in your case, 
x*-8, x*-10, x*-12 ...etc
3), square each numbers you got in the list
(x*-8)^2, (x*-10)^2, ... etc
4), add them up
5), divide them by the number of #s, in your case since you have
6 numbers, divide by 6

at this step, you will get a number called the "variant"
SD is defined as the square root of the variant, so

6), square root the number you got

yuki · Answer

rosette, do you need explanation how the formula works ?

anonymous · Answer

no