Which of the following statements is scientifically testable?

1. These alligators are scary.

   No. Being scary is not a physical property. Instead, it is an opinion. Some people might think they are scary, while other people might think they are not.

2. These alligators have sharp teeth.

   Yes! Careful observation would show that all three of these alligators have very sharp teeth. Anyone who put their hand into the mouth of these alligators would find out quickly that sharp teeth are a measurable, physical property that is scientifically testable.

   Remember that scientifically testable properties are going to be the same, no matter who tests them. For example, these alligators each have four legs, scaly skin, and lungs for breathing air. They are carnivorous, which means that they eat other animals. They are reptiles, and they lay eggs.

   All of that information is based on physical evidence that can be checked and verified. You could count their legs, examine their skin, etc. These things are scientifically testable.

   On the other hand, opinions are a property of the observer, not the object. I may think alligators are interesting. Someone else may thing they are scary, or ugly, or boring. You could test different people, to see if they think alligators are scary, but you can't test the alligator to see if it is scary. Opinions are not scientific evidence about the object.

3. These alligators have ugly eyes.

   No. Again, this is an opinion, not a measurable, physical property. I happen to think that alligators have pretty eyes.

4. These alligators are lazy.

   No. Lazy is not a measurable property. I might call them lazy, but you might think that they are just waiting for something tasty to walk by. Lazy is an opinion, and is not scientifically testable.

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I wanted to test a new fertilizer, to find the best concentration for my garden. I divided my garden into four sections and put a different amount of fertilizer in each section.

My test results showed that using 10 grams of fertilizer per gallon made the plants grow faster and bigger. To follow proper scientific guidelines, what should I do next?

1. Apply 10 grams of fertilizer per gallon to all the plants in my garden.

   No. While that might make my garden grow well, it would not provide more evidence that this was the best mixture of fertilizer

2. Do the same experiment over again.

   Yes! Repetition is an important part of the scientific process. If my hypothesis is correct, I should get the same results every time I repeat the experiment.

3. Do the same experiment, but use a different fertilizer.

   No. Using a different fertilizer would be testing a different variable. I wanted to find the best concentration of the original fertilizer, so testing a different fertilizer would not help with that.

4. Publish my results, so that other scientists could replicate my experiment.

   No. Replication is an important step, but I should repeat my experiment several times to be sure that I get consistent results before I ask other scientists to try replicating it.

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