This is a matched pair design. Input Group S into list, L₁ and Group N into list, L₂. Then place the differences into list, L₃. Finally perform a 1–sample t test on the differences (i.e., L₃).

1. Use TTest. Let α = 0.05. The hypotheses are: H₀: μ = 0 and H_a: μ ≠ 0. The P–value = 0.0229. Since P–value ≤ α/2, we reject H₀. This means there is a difference in the test results of the twins in the two different groups.
   
   
2. Use TInt. The 95% CI for the mean of the sample difference is –5.67 to –0.5799. Note that if you put Group S into list, L₂ and Group N into list, L₁, then your 95% CI for the mean of the sample difference is 0.5799 to 5.67.