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Interpreting Trends in ACT Science: Relationships Between Data Points

Posted by Dora Seigel | Jun 20, 2015 1:06:55 PM

ACT Science

 

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Interpreting trend questions can sometimes feel like looking into a crystal ball and predicting the future. Thankfully, no psychic powers are necessary to answer these questions. These questions do require you to interpret the data you are given, going beyond the basic factual questions. Interpreting Trends questions only appear in Data Representation and Research Summaries Passages. For more information about these types of passages and the other types of questions, check out the 3 types of ACT Science passages.         

Interpreting Trends questions ask you to evaluate graphs, tables, and/or scatterplots to decide if there is a relationship. Is it increasing or decreasing? Is there an inverse relationship or direct relationship? I'll go into more detail on this throughout this article. In this article, I'll transform you in a data interpreting whiz!

This is what I have in store for you:

  • Types of Interpreting Trends Questions:
    • 3 Kinds of Correlations tested on the ACT Science
    • Ranking Lists
    • ACT Science Practice Questions and Solutions

 

Types of Interpreting Trends Questions

3 Kinds of Correlation 

Direct Correlation

As one increases, so does the other, as one decreases so does the other. One direct relationship that most people have experienced is time sitting in the car on a road trip and the need to pee. The longer you drive, the larger your need to use the bathroom grows. Here is a sample graph of a direct relationship:

 

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While direct relationships are not always a line, it can be helpful to think of direct relationships as lines with a positive slope. As one increase, so does the other.

 

Inverse Correlation

As one increases, the other decreases. Shopping is a simple example, as you purchase more items, the amount of money you have decreases. Here is a sample graph of this inverse relationship:

 

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No Direct or Inverse Relationship

Here is a graph of data with no direct or inverse relationship:

 

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For this graph, try to describe this relationship in one word. You can’t. As you follow the trend, as temperature increases, density increases, but then it starts to decrease rapidly. So temperature and density are not inversely nor directly related.   

We will practice several ACT Science questions addressing these 3 types of relationships in the sample question section below, but first, let’s talk about the one other types of interpreting trends question. 

 

Ranking Lists

Sometimes the ACT will ask you to put data in increasing or decreasing order based on some criteria like height or mass. See a real ACT Science question below:

 

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I'll share my step by step thinking as I solve this question. To answer this question, you need to start by analyzing the question. What is the question asking you to find? These questions require extra analysis because you do not accidentally want to list the answers in decreasing order when they asked for increasing. In this question, they ask you to list the foods in INCREASING order for the amount of heat released per gram of food.

Now, we need to figure out which figures to use; the question says Tables 1 and 2. But which do we start with? This question actually requires you to look at the answer choices to figure out exactly what foods you are ranking.  

Note: on ranking questions, you do want to look at the answer choices before trying to solve the problem. The answer choices have useful clues. For this question, by looking at the answer choices, we know that we need to rank the four foods listed in Table 1 and sucrose (which is shown in Table 2). I would start with ranking the four foods in Table 1.     

Make sure you are looking at the correct column! The question asked about heat released per gram of food. We can see the mass is 1.0 g for all foods in Table 1. So we just need to look for heat released, which is the final column of the table. Ignore the column on change in water temperature; if you use it, you will possibly get the problem wrong.   

Now, double-check the ranking system, whether increasing or decreasing. The question said increasing order, so start with the smallest. According to Table 1, the increasing order should be potato, egg, bread, cheese. Knowing this, we can eliminate answer choices B and C because it ranks cheese before the other 3, which we know is wrong. To decide between A and D, we need to look at Table 2.

This is where mention of the heat released PER GRAM in the question becomes very important. This entire table analyzes heat released by glucose, but the amount of grams changes. Locate 1 g in the amount of sucrose column (it is the 3rd value from the top). The heat released by 1 g of sucrose is 16 kJ. Now, you need to place this in the appropriate location in the current rankings: potato, egg, bread, cheese.

Looking back at Table 1, see where 16 kJ fits in the heat released rankings. 1g of bread released 10 kJ and 1 g of cheese released 17 kJ. So, sucrose fits right in between. The final rankings should be potato, egg, bread, sucrose, cheese. The answer is A.

This is one of the more detailed ranking questions that I’ve ever come across in my teachings. It required you to synthesize two different visuals that were set up in very different ways. When approaching these questions, 

  • Start by analyzing the question. What is it asking you to find? What order? Increasing or decreasing?
  • Look at the answer choices for clues about what values you need to rank. 
  • Based on this information, decide which Figure you need to use. 
  • Make sure you are looking at the correct Figure. 
  • Use process of elimination. 
  • Make sure you have ranked the answer choices in the correct order, whether increasing or decreasing. 

If you mastered this ranking question, you will be able to master any ranking problem! Let’s tackle some more interpreting trends AT Science practice questions:

 

ACT Science Practice Questions and Solutions

Relationship ACT Science Practice Question #1

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To answer this question, start by figuring out what is asked of you, as we did in the ranking question. As the distance from the urban site increases, the question wants to know how the annual wet deposition changed for Cu and Zn. Now, let’s figure out which figure we need. The question said Study 3, so we need to use Figure 4 that accompanied Study 3:

 

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The key mentions 3 sites, but nowhere in Figure 4 does it list the distances. We have to skim for this information. In the last sentence of the paragraph above Figure 4, it says that Rural Site 1 is 50 km from the urban site and that Rural Site 2 is 100 km from the urban site.

Since the question wanted you to evaluate the annual wet deposition as distance from the urban site increased, start by ranking the sites in terms of increasing distance from the urban site: Urban site (0 km since it is the site), Site 1 (50 km), Site 2 (100 km).

Now, let’s start with one ion, Cu. As we progress from the urban site to site 1 to site 2, the bars get smaller, so the annual wet deposition decreases. So, for Cu as distance increases, annual wet deposition decreases. Knowing this, we can eliminate answer choices A, B, & D.

This only leaves us with C, which I think is the answer, but will double check by looking at Zn. As we progress from the urban site to site 1 to site 2 for Zn, the bars get smaller again, so the annual wet deposition of Zn does decrease also. The answer is definitely C.

So the relationships in question are both inverse. As distance increases, annual wet deposition decreases for both Cu and Zn.

 

Relationship ACT Science Practice Question #2

Some relationship questions will work backwards. Take for instance this question:

 

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This question asks you to evaluate the relationship that is given in a table and make it into a graph. Start, as always, by figuring out exactly what you are being asked, and in this case, it is to illustrate the relationship between heat released and change in water temperature. Answer choice B shows a direct relationship, answer choice C shows an inverse relationship, and answer choices A and D show relationships that are neither inverse nor direct.

When you are asked to evaluate relationship, based on a table, I recommend first reordering the table in chronological order, see below:

 

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This allows you to better see the relationship. I also encourage you to draw arrows to indicate increasing or decreasing such as I’ve done below:

 

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I now know that it is a direct relationship, as change in water temperature increase, so does the heat released. I know the answer has to be B.

 

Relationship ACT Science Practice Question #3

Let’s check out a question with a very tricky graph:

 

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As always, start by analyzing the question. Does S “depend” on frequency at a “given” wavelength? ”Depend” is a fancy word that simply means are the variables related? Do they have a definable relationship, either direct or indirect? ”Given” is a fancy word to say across all values. So, the question is asking you to evaluate if S has a relationship with frequency across all intensity values?

The next step is to make sure we are looking at the right figure, in this case, there was only one, so phew that was easy. Here it is:

 

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Now, we need to locate S, and compare it to frequency. In such a complex graph, circling is your friend. See my artwork below:

 

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You'll notice all of the S values are vertical lines. What this means is as frequency changes, the intensity of S at any value (S 10^-8%, S 10^-2%, S 10^-1%, S 100% - it is fine to not understand what these values mean) remains the same. So we can eliminate, F and H because we know S does not increase, it stays the same. Now to decide between G and J, does S depend on frequency, well since it doesn’t change when frequency does, the answer is No. So, J is the answer.

Major takeaways, make sure you know what you are being asked, make sure you look at the right part of the graph, circle for clarity, and graphs of vertical or horizontal lines mean there is most likely no direct or inverse relationship.

 

Recap

There are 2 Types of Interpreting Trends Questions

  1. Relationship based questions
  2. Ranking questions

For both question types,

  • Always make sure you understand what relationship the question is asking about.
  • Look at the answer choices for clues about what values you are looking for. 
  • Based on this information, decide which Figure you need to use. 
  • Make sure you are using the right Figure(s)
  • Make notes or drawings at each step if that helps you
  • Use process of elimination
  • Double-check your work if you have time

 

What’s Next?

I hope you feel ready to interpret any trend (except personal trends because then you’d be psychic)! 

For future ACT Science study, I recommend checking out our other articles on the 3 Types of ACT Science passages to learn more about the other types of questions asked on the ACT Science section, factual questions to learn more about this question type and to practice your visual reading skills, and the best way to study and practice for ACT Science to make the most out of your limited study time.


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Dora Seigel
About the Author

As an SAT/ACT tutor, Dora has guided many students to test prep success. She loves watching students succeed and is committed to helping you get there. Dora received a full-tuition merit based scholarship to University of Southern California. She graduated magna cum laude and scored in the 99th percentile on the ACT. She is also passionate about acting, writing, and photography.



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