Collecting and recording data
Before we can draw any graph, we must collect data. Data simply means information , usually counts or measurements. We collect data by asking questions, counting, and writing down what we find.
What is this?
Imagine you want to know which fruit is most popular in your class. You ask each student: "What is your favourite fruit?" You write down the answer. After asking all 30 students, you have 30 pieces of data.
To make sense of all this, we organise it. The simplest way is a table with tally marks.
A tally mark is a small vertical line. Every time someone says a fruit, we put a tally next to it. After 4 tallies, the 5th tally is drawn across the previous 4, making a bundle of 5. This makes counting fast.
| Fruit | Tally | Number |
|---|---|---|
| Mango | ||
| Apple | ||
| Banana | ||
| Grapes |
Total = 10 + 8 + 7 + 5 = 30, matching our 30 students.
Once data is in this table, we can answer questions:
- Which fruit is most popular? Mango (10 votes).
- Which is least popular? Grapes (5 votes).
- How many more chose mango than grapes? 10 − 5 = 5.
Tally marks are not just for class surveys. Shopkeepers count items, cricket scorers count runs, traffic surveyors count vehicles , all with tally marks.
Worked examples
Example 1. A teacher counted the number of children who came to school each day in a week: Mon 28, Tue 30, Wed 25, Thu 27, Fri 26. Show in a table.
| Day | Number |
|---|---|
| Mon | 28 |
| Tue | 30 |
| Wed | 25 |
| Thu | 27 |
| Fri | 26 |
Example 2. From a survey, the favourite colours of 20 friends were: 8 chose blue, 5 chose red, 4 chose green, 3 chose yellow. Which is most popular?
- Blue (8) is the most popular.
Example 3. 25 students were asked for their favourite sport. Tallies: Cricket |||| |||| ||| (13), Football |||| || (7), Hockey |||| (5). Total = 25. ✓
Try it
- Show 8 in tally marks.
- Convert tallies to numbers: |||| |||| || = ?
- In a class of 40, 15 like vanilla and 25 like chocolate ice cream. Make a table.
- From data , Apple 12, Mango 18, Orange 10 , which fruit got the most votes?
- Count letters in the word "MATHEMATICS" and tally how many of each letter.
Hands-on
Class survey. Ask 10 family or classmates a simple question , favourite fruit, favourite colour, favourite cartoon. Tally the answers. Find the most popular choice.
Traffic count. Sit near a road for 5 minutes (with a grown-up). Tally each kind of vehicle that passes , car, two-wheeler, bus, auto, cycle. Which is the most common?