We enjoy the hummingbirds that visit our feeders. I am trying to find the mixture of sugar and water that they like the best.

Each day, I put out four feeders with different amounts of water and sugar. At the end of each day, I measure to see how much of each the hummingbirds drank. Which of the following is NOT an important part of this experiment?

1. One of the feeders should only contain water, with no sugar.

   No. This IS an important part of the experiment. The feeder without any sugar is the control. If the hummingbirds drink just as much pure water, it would indicate that the sugar is not important.

2. The feeders should be placed randomly every day.

   No. This IS an important part of the experiment. If you always put the same mixture in the same location, the results may be because the birds like that location instead of because they like the amount of sugar.

3. I should repeat this experiment every day for several weeks.

   No. This IS an important part of the experiment. The more times you repeat the same test, the more likely you are to get accurate results.

4. The different mixtures should be colored different colors with nontoxic food coloring.

   Yes. This is NOT an important part of the experiment. It would add a second variable to the experiment, which is a bad thing. You want everything to be the same for each sample, with the only difference being the amount of sugar. If you used different colors and different amounts of sugar, you would not know whether the results were due to the color or the sugar.

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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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