What is one method for testing a hypothesis in scientific investigations?

Conducting controlled experiments is a fundamental method for testing a hypothesis in scientific investigations. This approach involves creating a structured environment where one variable can be manipulated while all other variables are held constant. By isolating the effect of the variable being tested, researchers can observe the outcomes and determine whether the hypothesis is supported or refuted.

Controlled experiments are essential because they allow for clear comparisons between the experimental group (where the variable is changed) and the control group (where the variable remains unchanged). This helps to ensure that any observed effects can be attributed to the manipulation of the variable in question, thereby providing robust evidence that either supports or contradicts the hypothesis.

In contrast, developing a conclusion is a stage that comes after data has been gathered and analyzed; it is not a method of testing a hypothesis. Collecting unnecessary data may complicate the investigation and lead to inconclusive results, whereas ignoring previous research undermines the foundation of scientific inquiry by neglecting established knowledge and insights that could inform the current investigation. Thus, controlled experiments stand as the most reliable method among the given options for testing a hypothesis.