When either test can be applied to the same data,the z-test for comparing the means of two independent samples is preferable to the unequal-variances t-tests,especially when doing the test with computer assistance.

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The choice between a z-test and an unequal-variances t-test (also known as Welch's t-test) depends on the known or assumed characteristics of the populations from which the samples are drawn. The z-test is appropriate when the population variances are known and the sample size is large. In contrast, the unequal-variances t-test is designed for situations where the population variances are unknown and assumed to be unequal, making it more appropriate in many real-world scenarios, especially with smaller sample sizes or unequal variances. Computer assistance does not inherently make the z-test preferable; it simply facilitates the calculation for either test.

When Either Test Can Be Applied to the Same Data,the