Statistics
Grade 1-2Bar Charts & Pictograms
Bar charts and pictograms are two of the simplest ways to display data, and exam questions test whether you can read values accurately, combine or compare them, and work with a pictogram key, including half symbols. This lesson covers reading values from a bar chart, finding totals and differences, reading a pictogram key, and working out how many symbols to draw for a given amount.
What you need to know
- Bar charts have equal-width bars with gaps, and the height shows the frequency.
- Leave gaps between bars for categories; a histogram for grouped data has no gaps.
- A pictogram needs a key showing what one symbol represents.
- Always label both axes and give the chart a title.
Written by Asad, co-founder of Teachably
Video walkthrough coming soon
The written lesson below covers everything you need in the meantime.
Reading values from a bar chart
Find the category on the horizontal axis, trace the top of its bar across to the vertical axis, and read off the value using the scale.
On a bar chart showing favourite fruit, the bar for Orange reaches up to 10 on the vertical axis, so 10 students chose Orange.
Finding totals and differences
To find a total, read off and add together the value for every category. To find a difference, read off the two values needed and subtract the smaller from the larger.
If Apple = 8, Banana = 5, Orange = 10 and Grape = 3, the total surveyed is 8 + 5 + 10 + 3 = 26, and 8 − 3 = 5 more students chose Apple than Grape.
Reading a pictogram key
A pictogram key shows what one full symbol represents. A half symbol represents half of that value, so multiply the number of symbols, including any half symbols, by the value of one symbol.
If each symbol represents 10 mm of rainfall, and Tuesday shows two and a half symbols, then the rainfall on Tuesday is 2.5 × 10 = 25 mm.
Working out how many symbols to draw
Divide the amount to be shown by the value of one symbol, then round the result to the nearest half symbol, since pictograms only use whole and half symbols.
If each symbol represents 10 pounds, and David saved £35, then 35 ÷ 10 = 3.5, so 3 full symbols and 1 half symbol should be drawn.
Worked examples
Three exam-style questions, fully solved
The bar chart shows the favourite fruit of a group of students. How many students chose Orange as their favourite fruit?
Easy- 1.Find the Orange bar and trace it up to the vertical axis: the bar reaches 10
Answer: 10 students
In a pictogram, each symbol represents 10 pounds. David saved £35. How many symbols (including any half symbols) should be drawn to represent this?
Medium- 1.Divide the amount by the value of one symbol: 35 ÷ 10 = 3.5
- 2.Round to the nearest half symbol: 3.5 symbols
Answer: 3 full symbols and 1 half symbol
The pictogram shows the rainfall recorded over three days, where each symbol represents 10 mm. How much more rainfall was recorded on Monday than Wednesday, if Monday shows 4 symbols and Wednesday shows 1 symbol?
Hard- 1.Find the rainfall for Monday: 4 × 10 = 40 mm
- 2.Find the rainfall for Wednesday: 1 × 10 = 10 mm
- 3.Subtract to find the difference: 40 − 10
Answer: 30 mm
Practice
6 questions, marked instantly
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Practice
Now try these yourself.
Type your answer and check it. The worked solution appears once you have had a go.
On a pictogram, a full circle represents 4 people. How many circles are needed to show 14 people?
On a pictogram, one symbol represents 10 books. A row shows 4.5 symbols. How many books does this row show?
A bar chart's vertical axis goes up in steps of 5. A bar reaches the third gridline above zero. What value does the bar show?
A bar chart has four bars with heights 8, 12, 6 and 10. Work out the total of all four bars.
On a bar chart, the blue bar has a height of 14 and the red bar has a height of 9. How much taller is the blue bar than the red bar?
A pictogram uses one symbol for 6 cars. A row has 2 full symbols and 1 half symbol. How many cars does this row show?
Avoid these
The mistakes students make most often
Misreading the scale on a bar chart's vertical axis, especially when the gridlines increase in steps other than 1, such as steps of 3 or 4.
Forgetting that a half symbol in a pictogram represents exactly half of the stated value, not always exactly one extra unit.
When finding a total from a bar chart or pictogram, missing out one of the categories or misreading one of the bars or symbol counts.
When working out how many symbols to draw, rounding to the nearest whole symbol instead of the nearest half symbol.
Multiplying the number of symbols by the wrong value, for example using the number of categories instead of the value stated in the key.
FAQ
Questions students and parents ask
Before this topic, make sure you know
What to learn next
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