What is data?
Data are the facts and measurements you collect in an investigation. The height of a plant each day, the number of birds at a feeder, or the temperature every hour are all data.
There are two main kinds:
- Numbers (quantitative data): 12 cm, 25 °C, 7 birds
- Descriptions (qualitative data): green, bumpy, smells sweet
Data on their own are just a jumble. To understand them, we organize them.
Collecting data
Before you start, decide:
- what you will measure or count
- what unit you will use
- how often you will collect data
Then record your data right away, so you don’t forget or mix things up.
Tally charts
A tally chart is a quick way to count. Draw a line for each thing you count. Every fifth line crosses the other four, which makes counting easy.
| Bird | Tally | Total |
|---|---|---|
| Robin | IIII I | 6 |
| Sparrow | IIII IIII | 9 |
| Blue jay | III | 3 |
Tables
A table organizes data in rows and columns. Give each column a heading with its unit.
| Day | Plant height (cm) |
|---|---|
| 1 | 2 |
| 3 | 4 |
| 5 | 7 |
| 7 | 10 |
Bar graphs
A bar graph compares amounts in different groups. Each bar stands for one group, and the length of the bar shows how many. Bar graphs are great for answering "which is most?" or "which is least?" In the bird data, the sparrow bar would be tallest.
Parts of a good bar graph:
- a title
- labels on both axes
- a scale that goes up evenly, such as 0, 2, 4, 6
- bars of equal width with equal gaps
Line graphs
A line graph shows how something changes over time. You plot a point for each measurement and join the points with a line. The plant data above would make a line graph that goes up and to the right, showing the plant is growing.
| Use a… | When you want to… |
|---|---|
| Bar graph | Compare separate groups |
| Line graph | Show change over time |
Finding patterns
Once your data are in a graph, look for a pattern. Does the line keep rising? Is one bar much taller than the others? Is there a value that doesn’t fit?
Drawing a conclusion
A conclusion answers your question using your data. A good conclusion says:
- what you found
- the data that show it
- whether your prediction was right
"The plant grew 8 cm in one week. The line graph went up steadily, so the plant grew a little every day. My prediction was correct."
Communicating results
Scientists share their results with others through reports, posters and talks. Graphs help people understand results quickly.
Common mistakes
- Uneven scales, such as 0, 1, 5, 20, which make graphs misleading.
- Missing labels or units.
- Using a line graph for separate groups, like favourite colours.
Try it yourself
- Count the cars that pass your window in 10 minutes. Sort them by colour in a tally chart.
- Turn your tally chart into a bar graph.
- Write one sentence describing a pattern.
- Write a conclusion: Which colour was most common?
Quick recap
- Data are facts and measurements.
- Tally charts help you count; tables organize data.
- Bar graphs compare groups; line graphs show change over time.
- Look for patterns, then write a conclusion that answers your question.
- Labels, units and even scales make graphs clear.