Final answer:
The correct answer is 'Rejection of hypothesis' since results that systematically contradict the null hypothesis provide evidence for its rejection and consideration of the alternative hypothesis.
Step-by-step explanation:
If the results of an experiment vary systematically in the opposite direction of the original hypothesis, this situation is typically described as a case where the null hypothesis may be rejected. The null hypothesis is an initial statement that there is no effect or no difference, and it is the default assumption that a hypothesis test seeks to challenge. When experimental results consistently contradict the predictions made by the null hypothesis, it provides evidence that could lead to the acceptance of the alternative hypothesis, which is a statement that proposes there is an effect or a difference. It's important to note that rejecting the null hypothesis does not necessarily prove the alternative hypothesis; it simply suggests that there is enough evidence to consider it over the null hypothesis.
Experimental error refers to a different concept within the context of hypothesis testing. It encompasses possible mistakes or uncontrolled factors that may affect the outcome of an experiment, thus potentially leading to incorrect conclusions. If an experiment's results are inconsistent with the null hypothesis, it does not necessarily mean that the experimental design was poor or incorrect; rather, new information has been uncovered that may require the formulation of a new hypothesis.
Therefore, the correct answer to the question is: Rejection of hypothesis.