How can you test a hypothesis about the difference between two independent population means with known standard deviations without using rejection regions?

Use the pooled sample variance and conduct an $f$-test to compare the population means

Use a confidence interval for the difference in means to determine if the hypothesized difference is plausible

Perform a paired sample $t$-test since the populations are independent

Use the sample standard deviations to estimate the test statistic and compare it to the chi-square distribution