Use more than one control group. Try a different experimental group. Change the hypothesis if it is incorrect. Repeat the procedure exactly the same each time.
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Which is the most reliable way to get unbiased results when conducting a controlled experiment?
Possibilities:
- Use more than one control group.
- Try a different experimental group.
- Change the hypothesis if it is incorrect.
- Repeat the procedure exactly the same each time.

Repeat the procedure exactly the same each time.