Classifying Statistical Data
9.1 Classifying Statistical Data – Cheat Sheet
1. Types of data
| Type of Data | Description | Examples |
|---|---|---|
| Qualitative | Non-numerical data | Colour of cars, type of fruit |
| Quantitative | Numerical data | Height, weight, age |
| Discrete | Countable values | Number of siblings, goals scored |
| Continuous | Measured values | Time, temperature, mass |
2. Grouped and ungrouped data
- Ungrouped → Raw data listed as individual values
- Grouped → Data organised into classes/intervals (e.g. 0–10, 10–20)
3. Frequency table
| Class Interval | Tally | Frequency |
|---|---|---|
| 0–10 | ||
| 10–20 | ||
| 20–30 |
4. Tally tables
- Used for counting occurrences quickly
- Every group of 5: four vertical lines with one diagonal line crossing them
Example:
|||| = 4
||||/ = 5
5. Two-way tables
Used to classify data according to two variables.
Example:
| Boys | Girls | Total | |
|---|---|---|---|
| Left-handed | 3 | 2 | 5 |
| Right-handed | 7 | 8 | 15 |
| Total | 10 | 10 | 20 |
6. Key points
- Always include a title and labels for rows/columns
- Add a Total row/column to check counts
- For grouped data, intervals should not overlap and should cover all values