Consideration is being given to purchase of two competing production systems. Performance of each machine is measured at random times. Sample sizes of 10 and 12 are obtained from each. What type of test should be implemented in this research?

Two-tailed Z test assuming unequal variances.

Two-tailed t-test, assuming equal variances and pooling variances weighted by sample size.

Two-tailed t-test assuming unequal variances.

One-tailed Z test assuming equal variances.