Here's why:

* The scientific method relies on testing: The core of the scientific method is to formulate a hypothesis, design an experiment to test it, and then analyze the results to either support or refute the hypothesis.

* A testable hypothesis allows for objective evaluation: If a hypothesis can be tested, it means there are observable and measurable outcomes that can be used to determine if the hypothesis is likely true or false.

* It helps to avoid speculation and bias: A testable hypothesis focuses on concrete observations and measurements, rather than subjective opinions or assumptions.

Key characteristics of a testable hypothesis:

* Specific: It clearly states what you expect to observe.

* Measurable: The outcomes can be quantified or observed.

* Falsifiable: It's possible to prove the hypothesis wrong through evidence.

Example:

Untestable hypothesis: "Dogs are better pets than cats."

Testable hypothesis: "Dogs are more likely to show signs of loyalty to their owners than cats."

The second hypothesis is testable because you could design an experiment to measure and compare loyalty behaviors in dogs and cats.