Choosing between a Z-test and a T-test isn’t hard once you know the rules. Sample size and known variance drive the decision. Get those right, and the rest falls into place. If you work with data, take a minute before running any test. Ask the right questions. Your results will be stronger, and your conclusions will hold up when it counts. If you want to practice, grab a small dataset and test both methods. Seeing the difference builds confidence fast.