Coaching Centre
Scientific reports and graphs
The sections of a scientific report and what goes in each, choosing a column graph or a line graph, drawing a graph properly, and writing a discussion and conclusion that use your evidence.
An experiment nobody else can read about might as well not have happened. Scientists share their work in a fixed format so that anyone, anywhere, can see exactly what was done, check the results, and try it themselves. Your school practical reports use the same format as a paper in a research journal.
The sections of a report
| Section | What goes in it | Example (ramp experiment) |
|---|---|---|
| Title | What the experiment is about | Ramp height and rolling distance |
| Aim | One sentence: what you are trying to find out. Usually starts "To find out…" or "To investigate…" | To investigate how the height of a ramp affects how far a toy car rolls. |
| Hypothesis | Your testable prediction with a reason (see 1A) | If the ramp is higher, then the car will roll further, because it starts with more energy. |
| Variables | IV, DV and the controlled variables (see 1E) | IV: ramp height. DV: distance rolled. Controlled: car, surface, release method. |
| Materials | A list of every piece of equipment, with sizes and amounts | Toy car, 1 m wooden plank, 4 textbooks, 5 m tape measure |
| Method | Numbered steps someone else could follow exactly, plus a scientific diagram of the set-up | 1. Rest one end of the plank on one textbook (10 cm high)… |
| Risk assessment | Hazards, the risk, and how you reduced it | Plank could fall on feet: keep it flat on the floor, stack books neatly. |
| Results | A results table and a graph. Observations only, no explanations | Table (1G) and a line graph |
| Discussion | Describe the pattern, explain it with science, discuss errors and how reliable and valid the results are, suggest improvements | "The higher the ramp, the further the car rolled…" |
| Conclusion | One or two sentences that answer the aim and say whether the hypothesis was supported | Raising the ramp increased the distance the car rolled, which supports the hypothesis. |
The aim and conclusion are a matched pair: if your aim is "To investigate how X affects Y", your conclusion must say how X affected Y.
Column graph or line graph?
A graph shows the pattern in your results at a glance. Which kind to draw depends on your independent variable.
| Column (bar) graph | Line graph |
|---|---|
| When the IV is in categories: names or types that have no in-between values | When the IV is numbers on a continuous scale: there are values in between your measurements |
| Type of surface (carpet, tiles, grass); brand of paper towel; type of chocolate | Ramp height (cm); temperature (°C); time (min); mass of sugar (g) |
| Columns don't touch; their order doesn't matter | Points are plotted and a line of best fit drawn through them |
The test: could you sensibly have a value halfway between two of your IV values? A ramp height halfway between 10 cm and 20 cm makes sense (15 cm). A surface halfway between carpet and tiles doesn't. So ramp height gets a line graph, surface gets a column graph.
Drawing a graph properly
- Title that says what the graph shows ("Distance rolled at different ramp heights").
- Independent variable on the x-axis (across), dependent variable on the y-axis (up). Remember: the DV goes up the side, just as it "depends".
- Label each axis with the quantity and the unit: "Ramp height (cm)".
- Choose an even scale on each axis (every square worth the same amount) that makes the graph fill most of the grid.
- Plot each point with a small, neat cross or dot. Use your averages.
- For a line graph, draw a line of best fit: a smooth line or curve that follows the trend, with points scattered evenly either side. Don't join the dots dot-to-dot.
- Pick a data set, decide whether it needs a column graph or a line graph, then plot it.
- For the line graphs, drag the line of best fit until it follows the trend. Which data set has an outlier?
Writing the discussion
This is where most marks are won and lost. Work through these in order:
- Trend: describe the pattern, using numbers. "As the ramp height increased from 10 cm to 40 cm, the distance rolled increased from 61 cm to 240 cm. Doubling the height roughly doubled the distance."
- Explain it with science: why might that happen?
- Errors and limitations: what could have affected the results? Releasing the car by hand might have given it a push; the car sometimes curved to one side.
- Reliability and validity: were the repeats close together? Were the variables really controlled?
- Improvements: specific changes that fix those problems. "Use a ruler as a starting gate and lift it so the car is released the same way every time."
Test yourself
Which section of a report contains numbered steps someone else could follow?
The method lets anyone repeat your experiment exactly.
An experiment compares how much water four brands of paper towel absorb. The best graph is a
Brand is a category. There's no brand halfway between two others.
An experiment measures how the temperature of water changes over 10 minutes of heating. The best graph is a
Time is continuous, so a line graph shows how temperature changes between readings.
On a graph, the dependent variable goes
IV across (x), DV up (y).
Which is the best conclusion for the aim "To investigate how the mass of a paper plane affects how far it flies"?
It answers the aim directly and refers back to the hypothesis.
A line of best fit should
It shows the overall pattern and smooths out small errors.
Put the sections of a scientific report in order.
Label the parts of the line graph.
Which graph would you draw for each independent variable?
A student's results: water at 10 °C dissolved a sugar cube in 95 s, at 30 °C in 52 s, at 50 °C in 30 s and at 70 °C in 18 s. Write a discussion paragraph that describes the trend using data, explains it, and suggests one improvement to the method.
As the temperature of the water increased, the time for the sugar cube to dissolve decreased: from 95 s at 10 °C to only 18 s at 70 °C, more than five times faster. This is because water particles move faster at higher temperatures, so they hit the sugar more often and harder, breaking it apart and spreading it through the water more quickly. Each temperature was only tested once, so the results may not be reliable. An improvement would be to do three trials at each temperature and calculate the average time.