⚠️ Standard error §

Formula §

Same variance §

$\sigma =$ standard deviation of population 1 & 2 $N_1=$ population size 1 $N_2=$ population size 2 $SE(x_1-x_2)=\sigma \sqrt{\frac{1}{N_1}+\frac{1}{N_2}}$

Different variance §

${\sigma }_1=$ standard deviation of population 1 ${\sigma }_2=$ standard deviation of population 2 $N_1=$ population size 1 $N_2=$ population size 2 $SE(x_1-x_2)=\sqrt{\frac{{\sigma }_1^2}{N_1}+\frac{{\sigma }_2^2}{N_2}}$