1. Calculate the mean \mu of the numbers:
\mu = \frac{28 + (-4) + 76 + 68 + 42}{5} = \frac{210}{5} = 42
2. Subtract the mean from each number and square the result:
(28 - 42)^2 = (-14)^2 = 196
(-4 - 42)^2 = (-46)^2 = 2116
(76 - 42)^2 = 34^2 = 1156
(68 - 42)^2 = 26^2 = 676
(42 - 42)^2 = 0^2 = 0
3. Sum the squared results:
196 + 2116 + 1156 + 676 + 0 = 4144
4. Divide by the number of data points to get the variance:
\sigma^2=\frac{4144}{5}=828.80
Answer:
828.80