Find the population variance and population standard deviation of the data set: 2, 4, 6, 8.
Solution
Problem
Find the population variance and population standard deviation of the data set: 2, 4, 6, 8.
Step 1: Find the population mean.
Mean = (2 + 4 + 6 + 8) / 4
Mean = 20 / 4
Mean = 5
Step 2: Find each deviation from the mean.
2 - 5 = -3
4 - 5 = -1
6 - 5 = 1
8 - 5 = 3
Step 3: Square each deviation.
(-3)^2 = 9
(-1)^2 = 1
1^2 = 1
3^2 = 9
Step 4: Add the squared deviations.
9 + 1 + 1 + 9 = 20
Step 5: Find the population variance.
Because the data represent the entire population, divide by N = 4.
Population variance = 20 / 4
Population variance = 5
Step 6: Find the population standard deviation.
The standard deviation is the square root of the variance:
σ = √5
σ ≈ 2.24
Therefore, the population variance is 5 and the population standard deviation is approximately 2.24.
Result
Population variance = 5; Population standard deviation ≈ 2.24