ACT Science: How to Compare Two Experiments

One type of ACT Science passage, Research Summaries, will present descriptions of one or more related experiments and will require you to answer questions about one or both experiments. To compare them accurately, answer the following questions as you read. Make sure to underline, circle, or otherwise mark up the passages as you read!

1. How is each experiment set up? Make sure you understand the method for each experiment. What tools/processes/chemicals are used?

2. What does the data show? Pay close attention to the results of each experiment. Usually this is presented in tables or charts. How do the different variables relate to one another? Draw arrows on the tables to show the trends. Keep the following definitions in mind:

Independent variables: These are factors that are controlled by the scientists. Did the scientists increase the heat in the experiment? Did they add or remove pressure? If the scientists have control over the variable, it is independent.

Dependent variables: These are factors that the scientists observe changing. This is what the look for and how they record data — but they don’t control it.

Direct variation: This is when two things change in the same way over time. If Column A increases and Column B increases at the same time, we can say that the two vary directly.

Indirect variation: If when Column A increases, Column B decreases, there is an indirect (also called inverse) variation between the two elements.

3. How do the experiments differ? There will be certain elements common to both experiments, and one or more elements will change from Experiment 1 to Experiment 2. Circle the new information. Then focus on the results – do the variables interact similarly or differently in the 2nd experiment? Is the range of data greater or smaller?

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