Answer
Variance is $\frac{62}{5}$
Standard deviation is 1.88
Work Step by Step
Step 1
First find the mean of the data set which is found by adding up all the numbers and dividing by the number of numbers.
2+5+6+7+-1+-1=18
18/6=3
Mean equals 3
Step 2
Variance is found by the equation
$\frac{(s1−M)^2+(s2−M)^2}{N−1}$
Where s is the sample
M is the mean and
N is the number of samples
So the final equation should look like
$\frac{((2)−3)^2+(5−3)^2+(6−3)^2+(7−3)^2+(−1−3)^2+(-1-3)^2}{6-1}$
Which equals 62/5
62/5 is the variance
Step 3
to find the Standard deviation or Sd
you take the square root of the variance
$\sqrt (62/5)$
Which approximately equals 1.88
The Sd is 1.88