Finding the variance

Variance quantifies how far apart a data set is. It is defined mathematically as the average of the squared deviations from the mean. To know the variance you should:

• Step 1: Calculate the mean (the simple average of the numbers).
• Step 2: Subtract the mean from each integer and square the result (the squared difference).
• Step 3: Calculate the average of the squared differences.

Example:

There are numbers 600, 470, 170, 430, and 300. Your first step is to find the mean:

Now, calculate each number's difference from the mean: 206, 76, – 224, 36, – 94.

To calculate the variance, take each difference, square it, and then average the result:

Answer: the variance is 21.704.