Difference random variable of 2 variables

Description:

• When $n$ tends to larger, ${\bar{x}}_1-{\bar{x}}_2\sim N(D_0,\sqrt{\frac{{\sigma }_1^2}{n_1}+\frac{{\sigma }_2^2}{n_2}})$
  • $D_0={\mu }_1-{\mu }_2$

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