Year 4 maths · Key Stage 2 · Statistics
Year 4 bar charts and time graphs: a guide for parents
In Year 4 children collect data, show it in charts and graphs, and answer questions about it. They work with bar charts and pictograms using bigger and less obvious scales, and they meet time graphs for the first time, which show how something changes over a period such as a day. They use what they read to solve comparison, sum and difference problems.
Bar charts and time graphs, explained
Data comes in two main kinds. Discrete data is counted and falls into separate groups, such as the number of children who chose each pet or the number of goals scored in each match. Continuous data is measured and can take any value along a scale, such as a temperature, a height or a length of time. Children in Year 4 are expected to present and interpret both kinds, and to pick a suitable graph for each. Bar charts and pictograms suit discrete data, where each bar or row stands for a separate category. Time graphs suit continuous data that changes over time.
Bar charts get harder in Year 4 because the scales do. Instead of each gridline meaning 1, a line might stand for 2, 5, 10 or 20, and some bars end between two labelled lines, so children have to work out the value halfway between them. In a pictogram one symbol might stand for 2 or 10 items, with a half symbol for half that amount. Children are also asked to draw charts of their own, choosing a sensible scale, labelling both axes and giving the chart a title.
A time graph is a line graph with time along the bottom and a measurement up the side, such as the temperature each hour. Each point is plotted and the points are joined with straight lines, because the measurement carries on changing between readings. Reading the graph tells a story: where it climbs, the quantity is rising; where it dips, it is falling; where it is flat, nothing changes. Children learn to read between plotted points to estimate values, though they are only estimates.
Most of the work is answering questions. A comparison question asks which is bigger or smaller, a sum question asks for a total, and a difference question asks how many more or fewer. The same questions are asked of tables, pictograms and graphs, so the real skill is reading the scale carefully, picking the right numbers and choosing whether to add or subtract.
Words your child will hear
- Bar chart
- A chart that uses bars of different heights or lengths to compare amounts.
- Pictogram
- A chart that uses pictures or symbols, where each symbol stands for a set number of items.
- Scale
- The numbers along an axis, which show what each gridline is worth.
- Axis
- One of the two lines on a graph that carry labels and numbers.
- Discrete data
- Data that is counted, in separate groups, such as the number of pets.
- Continuous data
- Data that is measured and can take any value, such as temperature or time.
- Time graph
- A line graph that shows how a measurement changes over time.
What the National Curriculum says
In Year 4, pupils should be taught to:
- Interpret and present discrete and continuous data using appropriate graphical methods, including bar charts and time graphs
- Solve comparison, sum and difference problems using information presented in bar charts, pictograms, tables and other graphs
Objectives from the National Curriculum in England, © Crown copyright, used under the Open Government Licence v3.0.
A worked example
A time graph shows the temperature in a garden. It was 6°C at 8 am, 9°C at 10 am, 13°C at 12 noon, 15°C at 2 pm and 12°C at 4 pm. How much warmer was it at 2 pm than at 8 am? Between which two readings did the temperature rise the most?
- First read the axes. Time is along the bottom, with readings every two hours. Temperature is up the side, so each reading is where the line crosses a time. List the five readings.
8 am 6°C 10 am 9°C 12 noon 13°C 2 pm 15°C 4 pm 12°C
- For the first question, find both readings. It was 15°C at 2 pm and 6°C at 8 am. A difference question means subtracting: 15 − 6 = 9.
- For the second question, work out the change between each pair of neighbouring readings. 8 am to 10 am is up 3 (9 − 6). 10 am to 12 noon is up 4 (13 − 9). 12 noon to 2 pm is up 2 (15 − 13). After 2 pm the line goes down by 3.
- The biggest rise is 4°C, which is the steepest part of the line before the peak. Check by looking at the graph: the steepest upward slope matches the biggest change.
It was 9°C warmer at 2 pm than at 8 am. The temperature rose the most, by 4°C, between 10 am and 12 noon.
Common mistakes and how to help
Counting every gridline as 1
In earlier years each square often stood for one item. In Year 4 the same gridline might be worth 2, 5 or 10, so a bar reaching 30 on a scale that goes up in 5s gets read as 6.
What helps: Before reading anything, find two labelled lines and work out the jump between them. Write the scale next to the chart in steps, such as 0, 10, 20, 30.
Reading a bar that falls between two lines as the lower number
Children read off the last labelled line the bar passed, so a bar halfway between 20 and 30 is called 20.
What helps: Ask what number is exactly halfway between the two lines (25) and whether the bar is above, below or at that point. Marking in the middle line helps.
Adding when the question asks for a difference
Questions such as ‘how many more’ do not contain the word ‘subtract’, and children grab the two numbers and add them.
What helps: Link ‘how many more’ and ‘how many fewer’ to the gap between two bars. Ask which bar is taller and by how much, then draw the gap on the chart.
Treating a time graph like a bar chart, or joining the wrong points
Children read each point as a separate category, or draw the line from the axis to a point rather than between points.
What helps: Remind them that time passes steadily between readings, so the points join up. Always ask: what is the axis showing, and does it change in between the readings?
How to help at home
- Run a family survey. Ask family and friends to choose a favourite fruit, film or sport. Tally the votes and draw a bar chart using a scale that fits the data, with a title and labelled axes.
- Chart the weather. Read an outdoor thermometer at the same times for a few days, or use a weather report. Plot the readings as a time graph and spot the warmest and coolest times.
- Ask questions about charts you meet. Newspapers, cereal boxes and sports tables use charts and tables. Ask how many more, how many fewer, and what the total is.
- Change the scale. Draw the same bar chart twice, once with each square worth 1 and once worth 5. Talk about why the second one is easier to read when the numbers are large.
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