chi squared

• calculate an expected value

  ratio is 9:3:3:1 (dihybrid)

  total number of organisms = 128

  1. add the ratio together (9 + 3 + 3 + 1 = 16)
  2. divide 128 by 16 = 8
  3. times each number in the ratio by 8
  4. eg: 9 x 8 = 72 (E)
• degrees of freedom

  always n - 1
• conclusions

  greater than critical value

  less likely the difference between expected and observed is due to chance

  reject null hypothesis