Living Environment Regents Practice Test

In an experiment on the growth of bacteria exposed to UV light, what can a valid hypothesis include?

1. If UV light is used, bacterial growth will stop

2. UV light exposure will not affect bacteria

3. Longer UV exposure reduces bacterial colonies

4. Bacteria will flourish under UV light

The correct answer is: Longer UV exposure reduces bacterial colonies

A valid hypothesis in an experiment is a statement that can be tested and is based on existing knowledge and observations. The chosen hypothesis suggests that longer exposure to UV light decreases the number of bacterial colonies, which is a testable statement. This hypothesis is valid because it establishes a clear relationship between two variables: the duration of UV light exposure and the growth of bacterial colonies. It can lead to specific predictions that can be measured and analyzed through experimentation, such as counting bacterial colonies at different exposure times to determine if they decrease, remain stable, or increase. On the other hand, the other options either suggest outcomes that are too definitive without allowing for varied observations or make claims that are not as easily tested. For example, the first option assumes a certain outcome without providing a range of variable conditions to measure. The second option asserts that UV light has no effect, which does not allow for investigation into varying levels of effect. The last option implies a positive growth under UV light, contrary to established scientific understanding that UV light typically harms bacteria.