Science: Data Representation for the ACT Exam

Common failure modes

These are the patterns that cause most candidates to lose marks on this topic. Recognising them in advance is half the work.

• !Misreading axis scales — especially when axes use scientific notation (×10³, ×10⁻⁶) or non-linear (logarithmic) scales
• !Interpolating values between data points without checking whether the relationship is linear — the question may provide enough information to verify linearity
• !Answering based on memorized science facts rather than what the provided data shows — ACT Science answers must come from the passage/figures, not from prior knowledge
• !Rushing through the introduction and missing key variable definitions that are needed to answer later questions

Study tips

• 1For every graph, read: (1) title, (2) x-axis label and units, (3) y-axis label and units, (4) what each curve/bar/line represents, (5) direction of relationships (positive, negative, or no correlation). Do this before reading the questions.
• 2Practice reading values from graphs with unusual scales (log scale, percentage, concentration in mM vs. µM). ACT regularly uses units that require attention.
• 3When a question asks you to predict a value beyond the graph range, identify the trend first (linear, plateauing, exponential) and apply it conservatively.
• 4Time yourself on Data Representation passages — they should take 3–4 minutes for 6–7 questions (faster than Research Summaries). Speed here buys time for the harder Conflicting Viewpoints passage.

Sample ACT Science: Data Representation questions

These sample items mirror the format and difficulty of real ACT questions. Practice with thousands more on the free Koydo question bank.

1. 1

   A figure shows a bar graph where bacteria growth (colony forming units per mL) is plotted for four temperatures: 10°C (500 CFU/mL), 20°C (1,200 CFU/mL), 30°C (2,800 CFU/mL), and 40°C (1,000 CFU/mL). Based on the figure, at which temperature did bacterial growth appear greatest?

   • A10°C
   • B20°C
   • C30°CCorrect
   • D40°C
   Why this answer?

   30°C shows the highest bar (2,800 CFU/mL) compared to all other temperatures. This is a straightforward data-reading question — identifying the maximum value from a bar graph. No knowledge of bacterial biology is needed; the answer is directly in the figure. (Illustrative.)

2. 2

   A table shows enzyme activity (units/min) at pH values 4, 5, 6, 7, 8: activities are 2, 8, 18, 32, and 28 respectively. If the trend continues, what is the best estimate for enzyme activity at pH 7.5?

   • A20 units/min
   • B28 units/min
   • C30 units/minCorrect
   • D35 units/min
   Why this answer?

   At pH 7, activity is 32; at pH 8, activity is 28. Interpolating halfway between pH 7 and pH 8 gives approximately (32 + 28)/2 = 30 units/min. This is a linear interpolation question — the most common "beyond-the-data" question type on ACT Science Data Representation. (Illustrative.)