Biology Foundations and Lab Skills Teaching Resources · High school biology; AP extensions where noted.
Use this original formative assessment after graphing practice. Students read values, compare changes, and distinguish a pattern from a causal explanation. Materials: the graphs or data below, paper, and a calculator if appropriate. Prerequisites: axes, units, line graphs, bar charts, and scatterplots.
Graph data and accessible alternative
The three datasets are simulated. The tables provide the complete values for students who use a screen reader or need a text alternative.
Graph preparation: construct the three graphs from the data tables below, then answer the questions. Use a line graph for A, bars for B, and a scatterplot for C. No external image is required.
| Graph A: time (days) | Height (cm) |
|---|---|
| 0 | 0 |
| 2 | 4 |
| 4 | 7 |
| 6 | 9 |
| 8 | 10 |
| Graph B: condition | Germinated seeds out of 20 |
|---|---|
| A | 8 |
| B | 14 |
| C | 11 |
| Graph C: leaf length (cm) | Leaf width (cm) |
|---|---|
| 3 | 1.5 |
| 4 | 2.0 |
| 5 | 2.1 |
| 6 | 3.0 |
| 7 | 3.2 |
| 8 | 4.0 |
Questions
- In graph A, which variable is on each axis, and what are its units?
- How tall is the seedling on day 4?
- Which two-day interval shows the greatest increase? Calculate that interval’s average increase per day.
- What is the average increase per day over the entire day 0–8 record? Does that mean the seedling increased by the same amount every day?
- In graph B, calculate the germination percentage for each condition.
- By how many percentage points does B exceed A? What additional design information is needed before claiming a treatment caused the difference?
- In graph C, describe the association. Would joining points in collection order clarify it?
- Does graph C establish that increased leaf length causes increased width? Explain.
Answer explanations
- Horizontal: time in days. Vertical: height in centimeters. Axis placement does not by itself prove a causal relationship.
- 7 cm, read at day 4.
- Day 0–2: (4 − 0) ÷ (2 − 0) = 2 cm per day, the largest interval average.
- (10 − 0) ÷ (8 − 0) = 1.25 cm per day. This overall average does not imply a constant daily rate; the interval increases differ, and no daily values between the plotted times were measured in the dataset.
- A: 8/20 = 40%; B: 14/20 = 70%; C: 11/20 = 55%.
- 70 − 40 = 30 percentage points. Need treatment definitions, comparable conditions, independent replication, and the assignment method to evaluate a causal interpretation.
- Longer leaves tend to be wider. Joining independent leaf measurements in arbitrary collection order would imply an order that the data do not have.
- No. This observational association does not identify a mechanism or rule out other influences.
Teaching notes: Award credit for supported reasoning and units, not a memorized phrase. Ask students to correct one misleading statement after review. Provide large-print graphs, oral explanation, or table-based access as needed. These explanations apply only to the new questions above; the former embedded quiz and placeholder are replaced.