Final answer:
The null hypothesis for Gaetan's experiment is that the new stain remover has no impact on grease stain removal compared to the old method. It is a default statement that assert there is no effect or difference until evidence suggests otherwise.
Step-by-step explanation:
The null hypothesis in Gaetan’s experiment would be that the new stain remover has no impact on removing grease stains from his pants compared to the current or old method he is using. The null hypothesis is a statement for an experiment that suggests there is no effect or no difference as a result of the treatment or change being tested. If Gaetan observes that the new stain remover does not perform any better than the old one, the null hypothesis cannot be rejected. If, however, the new stain remover appears to be more effective, Gaetan may have evidence to reject the null hypothesis and consider that his alternative hypothesis, which asserts that the new stain remover is more effective, might be true.