Two-tailed test

we want to know if the population mean difference $\mu_1-\mu_2$ is significantly different from 0 , in either direction.

confidence interval method: If the confidence interval for the population mean difference $\mu_1-\mu_2$ (cells B19 and B21) includes 0 (the population mean when the null hypothesis is true), accept the null hypothesis. Otherwise, reject it (the appropriate conclusion appears in cell B23).