How to Calculate a Student's T Test

Setting Up the Data Table

• 1

  Construct a table with four columns, with the first two columns for the first group (group A) labeled "x" and "x^2", and the last two columns for the second group (group B) labeled "y" and "y^2".

• 2

  List the raw scores, or numerical measured values, in the "x" and "y" columns for each member of the two groups.

• 3

  Square each value in column "x" and enter this number in the corresponding "x^2" column for group A. Do the same for each value in column "y".

• 4

  Add together and record the values for each of the four columns. Label the values "sum of x", "sum of x^2", "sum of y" and "sum of y^2".

• 5

  Count the number (N) of values or entries in column x and in column y. Record these values, labeled "Nx" and "Ny", in the appropriate column.

• 6

  Find the average value for the entries in column x and column y by dividing "sum of x" by "Nx", and "sum of y" by "Ny". Label these values as "Mx" and "My".

Initial Calculations

• 7

  Square the "sum of x" value and divide this number by the"Nx" value. Subtract this value from the "sum of x^2" value and label this result "C".

• 8

  Square the "sum of y" value and divide this number by the "Ny" value. Subtract this value from the "sum of y^2" value and label this result "D".

• 9

  Add the values for "Nx" and "Ny". Subtract 2 from this value and label "E".

• 10

  Add the reciprocal of the values of "Nx" and "Ny", or (1/"Nx") + (1/"Ny"). Label this value "F".

• 11

  Add the values of "C" and "D" together. Divide this result by the value for "E". Multiply this value by "F" and label this result "G".

Calculate the "T-ratio" or T-value

• 12

  Subtract the value of "My" from the value for "Mx". This number is the numerator for the "t-ratio".

• 13

  Take the square root of the value of "G". This number is the denominator of the "t-ratio".

• 14

  Solve for the t-test value by dividing the numerator value by the denominator value.