Evaluate Conclusions Against Evidence

Throughout history, people have made bold claims about the natural world. Some of those claims held up when tested; others crumbled under scrutiny. The ability to evaluate conclusions against evidence is the single most important skill in science — and it is heavily tested on the GED Science exam. Nearly every question on the test asks you to read a passage, look at data, and decide whether a conclusion makes sense. This skill did not appear overnight; it developed over centuries of scientific progress.

The central question this lesson addresses is straightforward: Does the evidence actually support the conclusion being made? On the GED, you will be given passages, graphs, tables, and diagrams along with one or more conclusions. Your job is to determine whether the data backs up those conclusions — or whether the conclusion goes beyond what the evidence shows.

Evaluating a conclusion against evidence is a structured process, not a guessing game. There are clear principles you can follow every time you encounter a scientific claim on the GED. These principles apply whether you are reading about biology, chemistry, physics, or earth science.

The diagram below shows the decision-making process you should follow every time you encounter a conclusion on the GED Science test. Start at the top by identifying the conclusion, then work through each checkpoint. This flowchart is your mental roadmap for evidence evaluation.

Notice that the flowchart has multiple possible outcomes. On the GED, you will not always be looking for a conclusion that is perfectly supported. Sometimes a question asks you to identify which conclusion is best supported, and the correct answer might only be partially supported — while the other choices are contradicted entirely. Learning to rank the strength of evidence-conclusion matches is key to getting these questions right.

Types of Evidence on the GED

The GED Science exam presents evidence in several forms, and you need to be comfortable with all of them. Quantitative evidence includes numbers, measurements, and data in tables or graphs. Qualitative evidence includes descriptions, observations, and characteristics that don't involve numbers. A passage might describe what happened during an experiment, while a data table shows the measured results. Both types count as evidence, and you need to consider both when evaluating a conclusion.

The Logic of Support

When you evaluate a conclusion, you are checking a logical relationship. Think of it this way: if the conclusion says "X causes Y," then the evidence should show that when X is present, Y happens, and ideally that when X is absent, Y does not happen. If the evidence only shows that X and Y occurred at the same time, the conclusion of causation is too strong — it should say "X is associated with Y" instead. This distinction between correlation (two things happening together) and causation (one thing directly causing another) is one of the most commonly tested concepts on the GED.

Signal Words That Indicate Conclusions

• Therefore — signals that a conclusion follows from the preceding evidence.
• This suggests / This indicates — signals an interpretation of data, not a raw fact.
• The results show that — introduces what the researcher believes the data mean.
• Based on the data / Based on the evidence — directly links a claim to data, making it easy to check.
• It can be concluded that — a formal conclusion statement often found in GED answer choices.

The GED test designers create wrong answer choices based on common mistakes people make when evaluating evidence. If you learn to recognize these errors, you will be able to eliminate incorrect answers quickly and confidently. The diagram below illustrates the most frequent reasoning errors and how to spot them.

When you read a GED question, ask yourself: "Is this conclusion making any of these five mistakes?" If so, it is probably a wrong answer. The correct answer will be the one that sticks closely to what the data actually show, without jumping to broader claims, confusing cause and effect, or ignoring parts of the data.

Let's walk through a GED-style example step by step. Read the passage and data table below, then follow how we evaluate the conclusion.

On the actual GED exam, you would not need to write all of this out for a multiple-choice question — but you would need to think through it quickly. For a short-answer question, you would write 3–7 sentences explaining your reasoning in a similar way, pointing to specific data and identifying any gaps.

Not all evidence is created equal. On the GED, you may need to judge whether the evidence presented is strong enough to support a particular conclusion. The table below compares characteristics of strong evidence with characteristics of weak evidence.

Evaluating conclusions against evidence does not exist in isolation. It connects to every other science practice tested on the GED. The table below shows how this skill relates to the other major science practices you need to master.

On the actual GED, you will sometimes see questions that combine multiple science practices in a single item. For example, a question might ask you to evaluate a conclusion (this lesson's skill) while also requiring you to interpret a graph (reasoning from data) and consider whether the experiment was well-designed (evaluating experimental design). Building strength in this core skill will help you across the entire test.