The most common passage type on the ACT Science test is the research summary. These passages make up about 45-60% of the test. In a research summary, you’ll read a short description of one or more experiments and look at the results.
A big part of these passages is analyzing and interpreting visual data, such as graphs or tables. You’ll also see questions about how the experiment was set up and why certain steps were included. Here is an example of one of these passages:
To do well on these passages, you need to answer questions about:
You can read more about these question types in their chapters of this textbook.
Some ACT Science passages can feel unfamiliar, and many questions can be answered by locating information directly in the passage or by comparing values in a graph or table. In those cases, you’re often not expected to fully understand the topic.
Research summary passages are often different. You’re expected to understand the purpose of the research and the reasoning behind key steps in the experiment. You should still start with the questions instead of reading the entire passage first, but you’ll usually need to look back more carefully to connect the setup to the results.
The goal is to test your understanding of the scientific method. The test evaluates your ability to form a hypothesis, identify a control group and variables, and draw a conclusion.
A hypothesis is a proposed explanation or prediction based on what we already know. It describes a possible outcome of the experiment. One possible hypothesis for the study in the sample passage could be that the rate of diffusion for solutions of NaCl would decrease in the presence of glucose molecules.
The independent variable is the variable the experimenter chooses to change. An independent variable in the study described by the sample passage is the percent NaCl.
The dependent variable is the variable that changes in response to the independent variable. You don’t directly change the dependent variable. A dependent variable in the study described in the sample passage is the rate of diffusion.
The control group is the baseline condition with no experimental change. You compare the other trials to the control group to see how much the results change. A control group in the study from the sample passage is the trial with the distilled water.
The conclusion is the statement you make based on the data you gathered. It summarizes the results and often supports or contradicts the hypothesis. One conclusion that could be made for the study in the passage would be that the presence of glucose decreases the rate of diffusion of 5% NaCl solution