Which of the following differences between two means is least likely to be statistically significant (assuming the variances of all groups are equal and each difference is tested using the same...

Which of the following differences between two means is least likely to be statistically significant (assuming the variances of all groups are equal and each difference is tested using the same alpha)?

(1) M₁ - M₂ = 2.47 and n = 10 for both groups. (2) M₁ - M₂ = 2.47 and n = 20 for both groups. (3) M₁ - M₂ = 2.47 and n = 30 for both groups. (4) M₁ - M₂ = 2.47 and n = 40 for both groups.