High School

Lab Study C: Making Predictions

Once the investigator has developed a testable hypothesis and a way to test that hypothesis, they can clearly state the predicted outcome that will either support or falsify the hypothesis. The prediction is always based on the particular experiment designed to test a specific hypothesis. Predictions are written in the form of if/then statements: "If the hypothesis is true, then the results of the experiment will be ..."; for example, "If extracts of marigold and rosemary are more effective than DEET in repelling insects, then there will be fewer bites on the arm sprayed with the plant extract compared to the arm sprayed with DEET after a 5-minute exposure to mosquitoes."

Making a prediction provides a critical analysis of the experimental design. If the predictions are not clear, the procedure can be modified before beginning the experiment.

For the butterfly experiment, the hypothesis was: "Infected monarch butterflies preferentially lay their eggs on plants that reduce parasite infection in their offspring." What should the prediction be? State your prediction.

To evaluate the results of the experiment, the investigator always returns to the prediction. If the results match the prediction, then the hypothesis is supported. If the results do not match the prediction, then the hypothesis is falsified. Either way, the scientist has increased knowledge of the process being studied. Many times the falsification of a hypothesis can provide more information than confirmation, as the ideas and data must be critically evaluated in light of new information.

In the butterfly experiment, the scientist may learn that the prediction is supported—there is a greater proportion of eggs on the milkweed plant with higher levels of antiparasite chemicals (A. curassavica). As a next step, the investigator may wish to examine the longevity of infected monarchs reared on A. curassavica compared with those reared on A. incarnata.

Return to page 4 and review your hypotheses for the numbered questions. Consider how you might design an experiment to test the first hypothesis. For example, you might separate a litter of kittens into two groups and raise them in two environments—one with human dander present and another where the air is filtered, removing human dander. The prediction might be: "If human dander causes allergic reactions in cats (a restatement of the hypothesis), then the cats raised in the environment with human dander will develop more allergies than those cats reared in a dander-free environment (predicting the results of the experiment)."

Now consider an experiment you might design to test the second hypothesis. How will you measure "acne outbreak"? State a prediction for this hypothesis and experiment. Use the if/then format.

The actual test of the prediction is one of the great moments in research. No matter the results, the scientist is not just following a procedure but truly testing a creative explanation derived from an interesting question.

Discussion
1. From this exercise, list the essential components of scientific investigations from asking a question to carrying out an experiment.
2. From this exercise, list the variables that must be identified in designing an experiment.
3. What are the components of an experimental procedure?

Answer :

Final answer:

To test a hypothesis in biology, one must create a prediction based on the hypothesis that is testable and falsifiable. The prediction stipulates what results are expected if the hypothesis is true. This step is essential before running experiments to validate or refute a hypothesis.

Explanation:

Testing the Hypothesis

To test a hypothesis, making a prediction is a key step. A prediction is a specific statement indicating the expected outcome under certain conditions. For instance, if the hypothesis is that infected monarch butterflies lay eggs on plants that reduce parasite infection in offspring, then the prediction could be: If infected monarch butterflies have a preference for laying their eggs on plants that reduce parasite infection, then we should observe a higher frequency of eggs on those plant species that have higher levels of antiparasitic compounds compared to those with lower levels.

Hypothesis Formation

A hypothesis is a proposed explanation based on scientific knowledge and must be both testable and falsifiable. This means that there must be a method to test the hypothesis with experimental data that could potentially support or refute it. For example, a hypothesis stating that human dander causes allergies in cats would lead to a prediction like: If human dander is causative for allergies in cats, then cats exposed to human dander should exhibit more allergic reactions than those in a dander-free environment.

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