Astronomers observed that the orbit of Uranus was not uniform. Therefore, they hypothesized the existence of another planet. This is an example of scientific investigation being led by . Inductive Reasoning
Deductive Reasoning

This is an example of scientific investigation being led by inductive reasoning.

Explanation:

Inductive reasoning is the type of reasoning used to make broad generalizations from specific observations. We have certain pieces of data and make conclusions based on them. In the given example, astronomers have made a specific observation - that the orbit of Uranus isn't uniform. Based on that fact, they made a broader conclusion - that there is another planet. There are probably more things that could lead to the same conclusion.

The opposite is deductive reasoning, where a person starts off with a broad generalization and tries to make specific, logical conclusions based on it.