How to Find the Variance in an ANOVA Test

SST

• 1

  Calculate the total of your data points. Sum all the data points in the study together. Call this value "T."

• 2

  Count the number of data points in the study. Call this number "N."

• 3

  Calculate the mean correction. The calculation for the mean correction is to square "T" and divide by "N." Call the mean correction "C."

• 4

  Compute the total of squared data points. Square all the data points in your study. Then add all of the squared data points together to arrive at a total. Call this total "T2."

• 5

  Find SST. SST is found by subtracting "C" from "T2."

SSB

• 6

  Sum the data points for each group in your study separately. Label the sums as "x1, x2, ..." for as many groups as are in your study.

• 7

  Square the sums. Go back to the numbers you just found and square them separately. Label the results "sx1, sx2, ..." for all the groups in your study.

• 8

  Find the number of data points in each group separately. Label these numbers "n1, n2, ..." for all the groups.

• 9

  Calculate SSB. Divide each "sx" value by its corresponding "n" value. Sum all of the resulting numbers and subtract the mean correction, "C," from the final result.

SSW

• 10

  Find SST. Use the method described in the section for SST.

• 11

  Find SSB. Use the method described in the section for SSB.

• 12

  Calculate SSW. Subtract SSB from SST.