ACT Science — three students, one data table: testing competing explanations against the evidence

ACT's third reporting category for the Science section, Evaluating Scientific Arguments and Models with Evidence, makes up 24 to 38 percent of the questions. ACT describes it as judging the validity of scientific information and formulating conclusions and predictions from it, for example deciding which explanation of a phenomenon is supported by new findings. On the test these questions often come in passages where three or more students or scientists offer different explanations of one observation, sometimes with a table of data alongside, and the questions ask you to hold all of them apart at once.

This material gives you two such passages, six questions each, with the three explanations and the data table printed in every question. In the first, three students disagree about what sets the period of a pendulum: length alone; length and mass; length and release angle. A table of five trials varies one factor at a time. In the second, three students explain a late-summer fish die-off in a pond: oxygen falling at dawn as an algae bloom grows, water that is simply too warm, or nitrate from fertilizer, with four weeks of temperature, dawn oxygen, algae cover, nitrate and fish deaths.

The questions cover the moves this passage type asks for. You pick the pair of trials that isolates the variable a student makes a claim about. You decide which student a set of results weakens, and notice that a student who says nothing about a variable is not weakened by it. You predict what one student's model implies, even when you believe a different model, and follow a mechanism such as a day-and-night oxygen cycle to its consequence. You find the single claim two students share. You choose the result that would pull two explanations apart, such as warm water kept full of oxygen, and test a new week of data against each student in turn. Every explanation says why each other option fails for that particular student.

The flashcards give a short method for multi-viewpoint passages: one line per student, isolate one variable, weaken versus support, apply the named student's rule, and check each student separately against every new result.

This material offers a quiz and flashcards. It is independent practice based on ACT's public description of the ACT Science section; the passages and data are original, and nothing here is produced or endorsed by ACT.

• Summarize three competing explanations as causes named and causes ruled out
• Choose the trials that isolate the variable a claim is about
• Decide which explanation a result weakens or supports, and recognize when an explanation is simply silent
• Predict what a given student's model implies and find the claim two students share
• Choose or evaluate a new result that distinguishes two explanations

Practice material written by Zestly, based on ACT's published description of the ACT Science section (reporting categories Interpretation of Data, Scientific Investigation, and Evaluating Scientific Arguments and Models with Evidence; act.org, retrieved September 2026). All data sets, figures and questions are original.