Reading Scientific Figures and Captions
Interpreting data displays, labels, captions, and visual evidence
Reading Scientific Figures and Captions
Interpreting data displays, labels, captions, and visual evidence
Science - Grade 9-12
- 1
A graph is titled "Effect of Temperature on Enzyme Activity." The x-axis is labeled "Temperature (°C)" and the y-axis is labeled "Reaction rate (mmol/min)." The line rises from 10°C to 37°C, reaches its highest point at 37°C, and then drops sharply by 60°C. Identify the independent variable, dependent variable, and the main trend shown.
Look at the axis labels and the pattern of the line.
The independent variable is temperature because it is shown on the x-axis and is the condition being changed. The dependent variable is reaction rate because it is measured in response to temperature. The main trend is that enzyme activity increases up to about 37°C and then decreases sharply at higher temperatures. - 2
A caption reads: "Figure 2. Average plant height after 21 days of growth under three light conditions. Error bars show ±1 standard deviation." What information does the caption add beyond the title of the figure?
The caption explains that the values are averages measured after 21 days, identifies the three light conditions as the comparison groups, and states that the error bars represent plus or minus one standard deviation. This helps the reader understand what the data points and error bars mean. - 3
A bar graph compares the number of bacterial colonies after treatment with four antibiotics. Antibiotic A has 120 colonies, B has 35 colonies, C has 80 colonies, and D has 10 colonies. The caption says lower colony count indicates greater antibiotic effectiveness. Which antibiotic appears most effective, and what evidence supports your answer?
Use the caption to decide whether a high or low value is better.
Antibiotic D appears most effective because it has the lowest colony count, 10 colonies. According to the caption, a lower colony count means greater antibiotic effectiveness. - 4
A figure legend includes the note: "n = 25 students per group." Explain what this tells the reader and why it matters when interpreting the figure.
The note means that each group in the study included 25 students. It matters because sample size affects how confidently a reader can interpret the data and compare groups. - 5
A scatter plot shows dissolved oxygen in a lake on the y-axis and water temperature on the x-axis. The points form a downward trend from left to right. What relationship does the figure suggest between temperature and dissolved oxygen?
A downward trend from left to right usually indicates a negative relationship.
The figure suggests a negative relationship between water temperature and dissolved oxygen. As temperature increases, dissolved oxygen tends to decrease. - 6
A map uses darker shading to represent higher nitrate concentration in groundwater. The caption states: "Samples were collected from wells in April 2024." What should a reader avoid concluding from this figure alone?
Pay attention to where and when the data were collected.
A reader should avoid concluding that nitrate levels were the same throughout the entire year or that the map proves the cause of the nitrate contamination. The caption shows the data come from well samples collected at one time, April 2024. - 7
A figure shows two lines: a solid line for Group 1 and a dashed line for Group 2. The key identifies the line types. Why is the key important for interpreting the figure?
The key is important because it tells the reader which line represents each group. Without the key, the reader could not accurately compare Group 1 and Group 2 or describe their trends. - 8
A graph's y-axis is labeled "Mass (g)" and runs from 48 to 52 instead of 0 to 52. The bars appear very different in height even though the values are close together. What should a careful reader notice?
Check the scale before judging the size of differences.
A careful reader should notice that the y-axis is truncated and does not start at zero. This can make small differences appear larger than they are, so the actual values should be read carefully. - 9
A caption reads: "The arrow indicates the direction of blood flow through the vessel." In the figure, the arrow points from left to right. How does the arrow help the reader understand the image?
The arrow shows the direction blood is moving through the vessel. This helps the reader interpret the process shown in the image rather than only identifying the structure. - 10
A data table lists pH values for four solutions: lemon juice 2.2, vinegar 3.0, pure water 7.0, and baking soda solution 8.3. The caption says lower pH means more acidic. Rank the solutions from most acidic to least acidic.
Sort the pH values from smallest to largest.
The solutions from most acidic to least acidic are lemon juice, vinegar, pure water, and baking soda solution. This order follows the caption because lower pH values are more acidic. - 11
A figure compares CO2 concentration over time at two sites. Site A has data from 2000 to 2020, while Site B has data only from 2015 to 2020. What limitation should be mentioned when comparing the two sites?
A limitation is that the two sites do not have the same time range of data. Site A has a longer record, so long-term trends at Site A cannot be compared directly with Site B for years before 2015. - 12
A microscope image caption says: "Scale bar = 10 µm." A cell in the image is about three scale bars long. Estimate the cell's length and explain your reasoning.
Multiply the number of scale-bar lengths by the value of one scale bar.
The cell is about 30 µm long because it is approximately three scale bars in length and each scale bar represents 10 µm. - 13
A figure caption states: "Values are means from three trials." Why might repeated trials be useful in a scientific investigation?
Repeated trials are useful because they reduce the influence of random error and make the average result more reliable. They also help show whether the pattern is consistent. - 14
A graph shows ice extent in the Arctic from 1980 to 2020. The line has year-to-year ups and downs but an overall downward trend. Write one accurate claim based on the figure.
Describe both the overall pattern and the smaller fluctuations.
An accurate claim is that Arctic ice extent generally decreased from 1980 to 2020, even though there were some year-to-year increases and decreases. - 15
A student writes, "The graph proves that fertilizer caused the plants to grow taller." The figure shows taller average plants in the fertilizer group than in the no-fertilizer group, but the caption does not describe random assignment or controlled conditions. Revise the student's statement to be more scientifically cautious.
Avoid claiming causation unless the figure and caption support it.
A more cautious statement is that the fertilizer group had taller average plants than the no-fertilizer group in the figure. The figure suggests an association, but more information about the experimental design is needed before concluding that fertilizer caused the difference.