Eine Validierungsstichprobe wurde zurückgehalten zur

You will mostly see this in technical reports or academic papers. It usually starts the sentence. You follow the word zur with a noun that explains the purpose. For example, you might say zur Modellprüfung (for model testing). It sounds very professional and precise. You are telling your audience that you didn't cheat on your homework. You kept a secret stash of data to verify your findings.

Use this in a professional setting. It is perfect for meetings about machine learning or laboratory results. If you are a developer, use it to explain your testing phase. If you are a scientist, use it in your methodology section. It signals to others that you follow a rigorous process. It is a hallmark of the C1 level because it handles complex passive structures and specific terminology.

Do not use this at a casual dinner party. If you tell a friend you 'withheld a validation sample' of the wine, they will think you are a robot. It is far too stiff for emotional conversations. Avoid it when you are talking about people or feelings. It is strictly for objects, data, and scientific processes. Using it in a bar might get you some very confused looks.

Germany is world-famous for its engineering and scientific rigor. This phrase reflects that cultural obsession with Gründlichkeit (thoroughness). In German culture, proving your work is just as important as doing the work. The concept of a Stichprobe (random sample) is a staple of German quality control. It is part of the 'Made in Germany' mindset of double-checking everything.

You might hear Rückstellprobe in the food industry. That is a physical sample kept in case someone gets sick. In data science, people might say Testdaten wurden separat aufbewahrt. However, Validierungsstichprobe is the gold standard for formal documentation. You can also change the verb to aufbewahren (to keep/store) if you want to sound slightly less like a textbook.