📊 Data & Charts

Collect, display and interpret data using charts and diagrams!

📖 Learn
Tally, pictogram, bar chart

✏️ Examples
Worked problems

🔬 Visualiser
Build bar charts

🎯 Practice
20 mixed questions

📖 Data & Charts

1. Tally Charts

Tallies record data one mark at a time. Every 5th mark goes across the previous 4 (a "gate").

IIII = 4 ||||‌~~||||~~ = 5

Count the gates (×5) and add remaining single marks.

Example: IIII II = 5 + 2 = 7

2. Pictograms

Each symbol represents a fixed number (the key). Multiply symbols by the key value.

Count = number of symbols × key value

Example: key = 2. Sport has 5 symbols → 5 × 2 = 10 students

Half a symbol = half the key value.

3. Bar Charts

Each bar's height shows the frequency. Read the scale on the y-axis carefully.

From a bar chart you can find: total, most/fewest, difference, range.

Range = highest value − lowest value

4. Carroll Diagrams

A Carroll diagram sorts data into 2 criteria (yes/no for each). Makes a 2×2 table.

Example: Even / Not even × Greater than 10 / Not greater than 10.

Each number goes in exactly one cell.

5. Venn Diagrams

Two overlapping circles. Numbers in the overlap satisfy both conditions. Numbers outside both circles satisfy neither.

A only | Both A and B | B only | Neither

Total = A only + Both + B only + Neither

✏️ Worked Examples

Example 1 – Reading a tally

Count: IIII IIII II

First group IIII = 5

Second group IIII = 5

Two singles II = 2

Total = 5 + 5 + 2 = 12

Example 2 – Pictogram

Key: 1 symbol = 2 students. Cricket has 3 symbols. How many students?

3 symbols × 2 = 6 students

How many symbols for 16 students?

16 ÷ 2 = 8 symbols

Example 3 – Bar chart range

Books read per day: Mon 4, Tue 8, Wed 6, Thu 10, Fri 12

Highest = 12 (Friday)

Lowest = 4 (Monday)

Range = 12 − 4 = 8

Example 4 – Venn diagram

Circle A: multiples of 2. Circle B: multiples of 3. Numbers 1–20.

Multiples of 2: 2,4,6,8,10,12,14,16,18,20 → 10 numbers

Multiples of 3: 3,6,9,12,15,18 → 6 numbers

Both (mult of 6): 6,12,18 → 3 numbers (in overlap)

Only A: 10−3 = 7 Only B: 6−3 = 3

🔬 Bar Chart Builder

Weekly Book Reading Chart

Mon=4, Tue=8, Wed=6, Thu=10, Fri=12, Sat=8, Sun=2

Exercise 1 – Counting Tallies

Count each tally and write the total.

Exercise 2 – Pictogram (key: 1 symbol = 2 students)

Use the pictogram data: Football=5 symbols, Cricket=3, Tennis=4, Swimming=7, Badminton=2.

Exercise 3 – Bar Chart

Books read per day: Mon=4, Tue=8, Wed=6, Thu=10, Fri=12, Sat=8, Sun=2.

Exercise 4 – Carroll Diagram

Numbers 1–10 sorted: even/odd AND greater than 10/not. Second diagram: multiples of 3.

Exercise 5 – Venn Diagram (multiples of 2 and 3, numbers 1–20)

Circle A = multiples of 2. Circle B = multiples of 3. Numbers 1–20.