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How to Calculate Variance

Finding variance in a data set doesn't require a mathematician. Impress your employer or teacher with your knowledge of statistics without the headache of complicated computations or formulas.


  • Step 1: Find the sum of the numbers Add all of the numbers together to find the sum.
  • Step 2: Divide the sum Divide the sum of the data by the number of values in the set to find the mean, or average.
  • TIP: For example, if the sum of 15 numbers is 300, dividing 300 by 15 you find that the mean is 20.
  • Step 3: Subtract the mean from each value Subtract the mean, or average, from each value in the data set and then square the difference, or multiply the result by itself.
  • TIP: For example, if a value of 32 is in the example data set, subtract 20 from it, and square the result. The result is 12 squared, or 144.
  • Step 4: Add the squared results Add all of the squared results together using a graphing calculator.
  • Step 5: Divide by the number of values Divide by the number of values in the data set. This will give you the variance of the data. Use this value to compare variances, make predictions, and show off how well you analyzed the data.
  • FACT: Sir Ronald Aylmer Fisher, known as the "Father of Modern Statistics," was a statistician and geneticist, and derived the concept of analysis of variance.

You Will Need

  • Set of data
  • Basic math computation skills
  • Graphing calculator

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