Updated August 21, 2026

4 ACT Science Strategies for Predicting Experiment Results

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Some ACT Science questions will ask you to predict experimental results. 

How are you supposed to do that without being able to recreate the experiment? It’s all about using the data you have to find the data you don’t. 

Based on more than 20 years of ACT Science tutoring experience, we’ve put together the key strategies just for this tricky question type. 

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Jump to section:
What’s a “Predicting Results” question on ACT Science?
Strategy Tip #1: Use key words to scan the passage and data
Strategy Tip #2: Start with the cause-effect relationship 
Strategy Tip #3: Interpolate or extrapolate to predict results 
Strategy Tip #4: Break up complex questions into multiple steps
Next steps

What’s a “Predicting Results” question on ACT Science?

Questions about Predicting Results on ACT Science will ask you to predict the results of an experiment based on the results of other experiments. They might also ask you how the results would change if you changed something about the experimental design.

Typical Predicting Results questions might look like this:

  • Based on the results of Experiment 1, if Experiment 2 were repeated except that all the piglets were fed Diet R instead of Diet Q, would the average body mass more likely have been lower or higher for each group?
  • Suppose that, in an additional trial of Experiment 1, a pH of 7 was tested. The time to hydrolysis of 100% of AG in this trial would most likely have been between:

Predicting Results is one of the ACT Science question types that you’ll see on Research Summaries passages. And Research Summaries refers to one of the 3 passage types on the ACT Science section. 

Each Research Summaries passage will describe the design of an experiment (usually 2 or 3 variations on a similar experiment), then provide the results of the experiment in the form of figures. You can find strategies and tips for approaching Research Summaries passages right here.

These questions are challenging, but luckily, there are key strategies that can help you ace them.

Strategy Tip #1: Use key words to scan the passage and data

Unlike for some ACT Science questions, you will need information from the passage to answer prediction questions.

But that doesn’t mean you need to understand the experiment in detail. On ACT Science, you have 40 questions to answer in just 40 minutes, which means you don’t want to waste any time reading in more detail than you need. (For time management tips, check out our guide to the ACT Science section, along with ACT strategies that work for any question type.)

Instead, skim the passage. Jot down notes next to each experiment described:

  • What’s being varied in this experiment?
  • How is it different from the other experiment(s) described?

Then, move on to the questions. Use the question to guide a closer look at the passage. Say you get a question like this:

Suppose that, in an additional trial of Experiment 1, a pH of 7 was tested. The time to hydrolysis of 100% of AG in this trial would most likely have been between:

Don’t read the passage from start to finish. Instead: 

  • Ask yourself what’s being changed. Here, it’s the pH.
  • Now scan for that key word. Where do you see data about the effect of pH? Start there.

Strategy Tip #2: Identify the cause-effect relationship

Predicting experimental results is all about understanding cause and effect. You want to identify how the experiment is changing and what effect that will likely have, based on the data.

Before you get into the nitty-gritty of the data, ask yourself:

  • What variable are we looking at?
  • What effect does that variable have?
  • What’s the effect of changing it? 

As you read the question, underline or circle how the experiment is changing. That’s the variable we’re interested in.

Based on the results of Experiment 1, if Experiment 2 were repeated except that all the piglets were fed Diet R instead of Diet Q, would the average body mass more likely have been lower or higher for each group?

F. Lower; on average, piglets fed Diet R had an average body mass 20 percentile points greater than those fed Diet Q.
G.  Lower; on average, piglets fed Diet R had an average body mass 10 percentile points smaller than those fed Diet Q.
H. Higher; on average, piglets fed Diet R had an average body mass 10 percentile points greater than those fed Diet Q.
J. Higher; on average, piglets fed Diet R had an average body mass 20 percentile points greater than those fed Diet Q.

Piglets’ dietAverage body mass (percentile of control group body mass)
Q45
R65
S75
T55
  • What variable are we looking at? We’re looking at the piglets’ diet – specifically, Diet R versus Diet Q.
  • What effect does that variable have? We can see from the data that Diet Q leads to a lower average body mass (45th percentile) than Diet R (65th percentile). 
  • What’s the effect of changing it? If we change the piglets’ diet to R instead of Q, we can expect their average body mass to go up.

 Here’s the cause-effect relationship:

Piglets eat diet R → piglets get heavier; piglets eat diet Q → piglets get lighter. 

So if we switch all the piglets to Diet R, we can expect average body mass to go up. That eliminates answers F and G.

Now, use the process of elimination to choose between answers H and J. The only difference is something you can easily verify in Table 1: how much greater is the average body mass on Diet R than on Diet Q?

On Diet R, the average body mass was in the 65th percentile. On Diet Q, the average body mass was in the 45th percentile. So 65 – 45 = 20 percentile points difference. That’s answer choice J.

Strategy Tip #3: Interpolate or extrapolate to predict results

Some questions will ask you to predict specific experimental results. These won’t involve complicated math (which is good news, since you may not use a calculator on ACT Science). 

Instead, you’ll need to use the data you have to find the data you want.

Suppose that, in an additional trial of Experiment 1, the experiment was ended after 30 minutes. The % hydrolysis of D in this trial would most likely have been between:

F. Below 50%
G. Between 50% and 60%
H. Between 60% and 70%
J. Over 70%

Before you try to understand the experiment in detail, start by looking at the data.

Ask yourself:

  • What variable are we looking at? What’s being changed is the time, the duration of the experiment.
  • What effect does that variable have? The longer the duration, the more D is hydrolysed.
  • What’s the effect of changing it? Reducing the time will reduce the % of D hydrolysed.

Now that you have that cause-effect relationship, locate the precise answer in the data. Here, you’re interpolating: the range you’re interested in is within the range of the data. 

Draw on the graph to pinpoint the data you’re after: after 30 minutes, what percentage of D was hydrolysed? The answer is a little under 60%, so you want answer choice G.

For more practice, here are 9 of the hardest ACT Science questions out there, along with detailed explanations for each one.

Strategy Tip #4: Break up complex questions into multiple steps

More complicated ACT Science questions will have multiple steps. You’ll need to find more than one piece of data – often from different figures – and use both to find the answer.

Remember that easy and difficult questions are worth the same number of points on the ACT, so start with easier questions and save trickier ones for last. (Here’s our ACT score calculator with more info about how the test is scored.)

Based on the results of Experiments 1 and 2, the % of D hydrolysed would likely be the greatest for which of the following combinations of temperature and duration?

F. temperature: 30 °C
duration: 60 min
G. temperature: 70 °C
duration: 60 min
H. temperature: 30 °C
duration: 120 min
J. temperature: 70 °C
duration: 120 min

If you were annotating as you skimmed the passage, you would have identified the figures that show the effect of temperature and duration:

Figure 1 shows the effect of time:

Figure 2 shows the effect of temperature:

Now, break the question into multiple parts.

  • After what duration is the greater % of D hydrolysed: 60 min or 120 min?

Based on Figure 1, it’s 120 min, so you can eliminate answers F and G.

  • At what temperature  is the greatest % of D hydrolysed: 30 °C or 70 °C?

Based on Figure 2, it’s 70 °C, so you can eliminate answer H.

By the process of elimination, you’re left with answer J.

For more practice using strategies like this, you might want to use an ACT prep book (we’ve researched the 11 best ones out there) or make a personal ACT prep plan. For even better results, consider working with a specialized test prep tutor. Give us a call to talk about what kind of ACT tutoring would work best for you.   

Next Steps

With these ACT Science strategies, you’ll be well prepared to tackle any question on predicting experimental results!

For more support mastering these strategies, an experienced ACT tutor can make a huge difference. We’ve been working with students preparing for the ACT for over two decades, and many of our tutors achieved perfect scores on the ACT themselves. Our students often see their scores go up by several points over just a few months of tutoring. Learn more about our programs here, and get in touch with our team for a free consultation on the right option for you.

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Ro

Rosamond graduated summa cum laude from Princeton. During college, she worked as a peer tutor for Italian, French, Greek, and academic writing. Since graduation, she’s continued to tutor students of all ages in French, Italian, Latin, English, and math, some of them for several years. She’s currently a graduate student studying the relationship between religion and secular law, and she works as a freelance journalist and translator.

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