What is the difference between 试验 and 实验?
实验 is used for operations and activities done to test a scientific theory or hypothesis. An example: 经过反复实验，证明这一结论是正确的

试验 is used to inspect the function or effect of some physical thing (something that already exists). It's typically done in some lab.
Some examples:


新农药要经过反复试验才能推广
试验新机器
新办法试验后推广