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Comparing Two Hypotheses on the ACT Science Test

Hypothesis questions can occur on different parts of the ACT Science Test. You’re definitely going to see some ACT Science questions that ask about hypotheses on the Research Summaries passages, but hypothesis questions can also appear in Data Interpretation passages. You may be asked to compare hypotheses as well!


Comparing Hypotheses

When confronted with a hypothesis question, make sure to always examine the point of view of the student/scientist/author. Ask yourself whether the data supports their conclusions, or not. You may be asked to weaken or strengthen hypotheses individually, or you may be asked to compare more than one hypothesis.

To compare them, remember that you must understand the premise behind the experiments in order to know whether the results will weaken a conclusion. Try to identify the purpose, method, and results for each experiment first to get better scores on hypotheses questions. Unless you know the purpose, method, and results and can step into the scientists’ perspectives you will have a difficult time understanding the hypotheses. Once you’ve figured out one scientist’s perspective, quickly jot down some notes so you won’t forget as you move on to the next scientist’s point of view. This can save valuable time and help prevent you from re-reading the same information over and over again.



Here is a harder practice ACT Science Research Summaries passage, just like you might see on Test Day!


Astronomers observing a nearby galaxy have measured the position of the “turnoff” in a 25 globular clusters.  If the turnoff occurs at the same spectral class in different globular clusters, those clusters must be of approximately the same age.  Furthermore, if most of the clusters in a galaxy are of similar ages, the galaxy itself may be of that age.  Figure 2 shows the number of clusters with turnoffs in each spectral class.

Do the figures support the hypothesis that most of the globular clusters in the galaxy in Figure 2 are of similar ages?

A – No, Figure 2 shows that the clusters in the galaxy have different turnoffs, and thus different ages

B – No, Figure 2 shows that the turnoffs of the clusters vary from A to K in spectral class, and these clusters thus vary widely in age

C – Yes, Figure 2 shows that most of the clusters in the galaxy have a turnoff in spectral class G, and are thus similar in age

D – Yes, Figure 2 shows that all of the clusters in the galaxy have a turnoff, and are thus similar in age



We know this is a question asking us to understand and compare hypotheses because of the phrase “support the hypothesis.” The data we have to focus on is the “ages” of the “globular clusters” in “Figure 2.” Figure 2 shows that most of the clusters, 20 out of 25, have turnoffs in the same spectral class (G). The passage states that if the turnoffs in different clusters are in similar locations, the clusters are of similar ages. Thus, these 20 clusters are similar in age. The answer is (C).


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