Find the variance and standard deviation for the following set of data:

101,102,100,100,110,109,109,108,109

I've tried a hundred different ways to solve this and I can never get an accurate answer. Can someone please explain this to me? Thanks (:

Question

Find the variance and standard deviation for the following  set of data:

101,102,100,100,110,109,109,108,109

I've tried a hundred different ways to solve this and I can never get an accurate answer. Can someone please explain this to me? Thanks (:

amistre64 · Answer

we can make this less daunting by moving the range of values to more workable values

subtract 100 from each value and it works out the same

amistre64 · Answer

$$X:\{x_1+k,x_2+k,x_3+k,...,x_n+k\}$$
$$mean(X):\frac{x_1+k+x_2+k+x_3+k+...+x_n+k}{n}$$
$$mean(X):\frac{(x_1+x_2+x_3+...+x_n)+kn}{n}$$
$$mean(X):\frac{(x_1+x_2+x_3+...+x_n)}{n}+k$$

1,2,0,0,10,9,9,8,9   what is the mean of this equivalent set?

amistre64 · Answer

moving the range of the data to something more workable doesnt change the variance, and since variance is the square of standard deviation, it doesnt alter the sd either

can you work the var and sd with this set now?

anonymous · Answer

Yes thank you (:

amistre64 · Answer

cool :)  if you still need help, feel free to ask