Question

What is the variance of {-7, 42, -5, 1, 6, -3, 4, -2, 17, 53, -2, 4, 7, 88}?

Answer 1

Population variance `705.11` (approx.)
Sample variance `759.35` (approx.)

Explanation:

Method 1: Use a Spreadsheet
Enter the data value in a column (or row)
and use the VARP(range) (for population variance) or the VAR(range) (for sample variance) function.

Method 2: Manual Calculation
Find the sum of the data values.
Find the mean value (by dividing the sum by the number of data values)
For each data value calculate the difference between it and the mean.
For each data value calculate the square of the difference between it and the mean.
Calculate the sum of the squares
For population variance, divide the sum of the squares by the number of data value; for sample variance, divide the sum of the squares by (1 less than the number of data values).

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Use Population Variance if the data represents all entities in the universe of discourse.
Use Sample Variance if the data represents a random selection of entities from the universe of discourse.