# Math Help - Standard deviation stuck

1. ## Standard deviation stuck

Hai ... i still stuck for the following questio. for your info i already do the calculation & my ans is 88.25 or 88.75.something wrong maybe on my calculation.

Question:
The standard deviation of 6,9,8,x and 12 is 2. Calculate the value of x.

tq for your time and help

2. Originally Posted by nikk
Hai ... i still stuck for the following questio. for your info i already do the calculation & my ans is 88.25 or 88.75.something wrong maybe on my calculation.

Question:
The standard deviation of 6,9,8,x and 12 is 2. Calculate the value of x.

tq for your time and help
Substitute the given data into the usual formula for standard deviation. Please show your working and where you get stuck.

3. Originally Posted by mr fantastic
Substitute the given data into the usual formula for standard deviation. Please show your working and where you get stuck.
tq for your response sir.. attached is my solution.. i don't where is wrong..

4. Originally Posted by nikk
tq for your response sir.. attached is my solution.. i don't where is wrong..
$s^2 = \frac{1}{5-1} \left(6^2 + 9^2 + 8^2 + x^2 + 12^2\right) - \frac{5}{5-1} \left( \frac{6 + 9 + 8 + x + 12}{5}\right)^2$
$s^2 = \frac{1}{5-1} \left(6^2 + 9^2 + 8^2 + x^2 + 12^2\right) - \frac{5}{5-1} \left( \frac{6 + 9 + 8 + x + 12}{5}\right)^2$