Revision notes
Ask a question, collect the answers, then use tally marks and a frequency table to see what they tell you.
Aunty Bisi, who runs the school canteen, asked 40 students what they like to eat. A long list of answers is hard to read — but once she counts them neatly, she can see at a glance that jollof rice wins!
Data is information we collect to answer a question, like “What is your favourite food?”.
We collect it by asking people (a survey), by counting (cars passing the school gate) or by measuring (heights of students).
Each answer is written down as it comes, so nothing is missed or counted twice.
🔑 Key idea: Start with a clear question, then collect every answer carefully.
A tally is a quick way to count. Draw one stroke | for each answer.
The fifth stroke goes across the first four to make a gate: ||||/ means 5.
Gates are easy to count in fives: ||||/ ||||/ ||| is 5 + 5 + 3 = 13.
🔑 Key idea: Each gate ||||/ is 5. Count the gates in fives, then add the single strokes.
The frequency of an answer is how many times it appears.
A frequency table lists each answer with its tally and its frequency. Adding all the frequencies gives the total number of people asked.
From the table we can quickly see the most popular answer (biggest frequency) and the least popular (smallest frequency).
🔑 Key idea: Frequency = how many times. All the frequencies add up to the total.
Musa asked 22 students how they get to school each morning. The answers were: car, keke, keke, car, keke, bus, okada, keke, bus, car, keke, car, bus, bus, car, keke, okada, okada, bus, okada, bus, keke. How many students said “car”?
Step 1: Tally as you read
car: ||||/
Why? Ticking off each answer as you tally stops you counting anything twice.
Step 2: Count the tally
car appears 5 times.
Answer: 5
Ready to check you've got it? Scroll up and work through the lesson: the interactive visuals, practice questions and mastery check are all there.