Pictograms (Edexcel GCSE Maths): Revision Notes
Pictograms
What is a pictogram?
A pictogram is a type of chart that uses pictures or symbols to represent data visually. It's an effective way to display information from tally charts or frequency tables in a clear, easy-to-understand format.
Pictograms are particularly useful because they make data more engaging and accessible than simple numbers alone. Each row typically represents a different category, and the number of symbols shows the frequency for that category.
Pictograms are especially popular in primary education and public displays because they can communicate complex data at a glance, making them accessible to people with varying levels of mathematical background.
Essential components of a pictogram
The key
Every pictogram must have a key. The key is crucial because it tells you exactly how many items each picture or symbol represents. Without a key, the pictogram would be meaningless.
Worked Example: Reading a Key
If the key shows that one television symbol = 2 people, then:
- 6 television symbols = 6 × 2 = 12 people
- 4½ television symbols = 4.5 × 2 = 9 people
Symbols and partial symbols
Pictograms can use partial symbols to represent data that doesn't divide evenly. If one symbol represents 2 people, then half a symbol represents 1 person.
When working with partial symbols:
- ¼ symbol = ¼ of the key value
- ½ symbol = ½ of the key value
- ¾ symbol = ¾ of the key value
Always pay careful attention to partial symbols in pictograms. A common mistake is to count partial symbols as whole symbols, leading to incorrect calculations.
Reading pictograms
To interpret a pictogram effectively, follow these essential steps:
- Check the key first - this tells you what each symbol represents
- Count the complete symbols in each row
- Account for partial symbols - add the fractional values
- Calculate the total by multiplying the number of symbols by the key value
Calculating totals from pictograms
To find the total number represented in the entire pictogram, add up the values from each category.
Worked Example: Calculating Total from Pictogram
If the categories show 12, 9, 2, and 7 respectively, the total calculation would be:
Step 1: List all category values 12 + 9 + 2 + 7
Step 2: Add them together Total = 30
Creating pictograms
When drawing a pictogram from given data, follow these key steps:
- Choose appropriate symbols that relate to your data
- Decide on a suitable key value - this should make your pictogram neat and manageable
- Draw complete symbols first, then add partial symbols where needed
- Include clear labels for each category
- Always include your key
Worked Example: Creating a Pictogram
To represent 10 items when your key shows 1 symbol = 4 items:
Step 1: Divide the data by the key value 10 ÷ 4 = 2.5 symbols needed
Step 2: Draw the symbols 2 complete symbols + ½ symbol
Step 3: Verify 2 × 4 + 2 = 8 + 2 = 10 ✓
Connection to tally charts
Tally charts work similarly to pictograms in representing frequency data. In tallies:
- Each mark represents 1 item
- Groups of 5 are shown as four vertical lines with a diagonal line through them
- To represent 12 items: you would draw two complete groups of 5 plus 2 individual marks
Both pictograms and tally charts are methods of organising and displaying frequency data, making it easier to analyse and interpret. The choice between them often depends on the audience and the type of data being presented.
Exam tips
Essential Exam Strategies:
- Always check that your pictogram includes a clear key
- When reading partial symbols, be careful with your calculations
- Show your working when calculating totals from pictograms
- In exam questions, read the key carefully before attempting calculations
- If creating a pictogram, choose a key value that makes sense for your data
Key Points to Remember:
- Every pictogram must have a key - this is essential for interpretation
- Partial symbols represent partial values - half a symbol = half the key value
- Add up all categories to find the total represented in the pictogram
- Choose sensible key values when creating pictograms to keep them neat and readable
- Pictograms and tally charts are both ways to represent frequency data visually