Which of the following is NOT a method for ensuring a fair experiment?

In scientific experiments, ensuring fairness is crucial for obtaining valid and reliable results. A method that is NOT considered a practice for ensuring a fair experiment is having fixed results. This method undermines the scientific process because fair experimentation requires that results be determined by the data collected during the experiment, rather than predetermined or fixed before the experiment takes place.

The other methods, such as employing a large sample size, random selection of samples, and double-blind testing, are established techniques used to mitigate biases and increase the reliability of the results. A large sample size helps to ensure that the results can be generalized to a larger population, random selection reduces selection bias, and double-blind testing helps to eliminate biases from both the participants and the researchers. These practices contribute to the integrity and credibility of scientific investigations.