Quantitative vs Qualitative data
Big Idea: Quantitative = numbers. Qualitative = descriptions or categories.
Quantitative: How much? How many? How long? Qualitative: What kind? Which category? What color?
| Type | Definition | Example |
|---|---|---|
| Quantitative | Measured in numbers | Height 175 cm, Temperature 22°C, Score 85% |
| Qualitative | Described by categories or words | Color: red/blue, Opinion: agree/disagree, Brand: Nike/Adidas |
IB term: Qualitative data is sometimes called 'categorical' in statistics.
Recognition tip: Can you count it or measure it precisely?
YES → Quantitative.
NO → Qualitative.
Free preview
This is the free notes preview
You're reading the free notes. Aimnova Pro unlocks the full study experience — and you can try it with your first topic free to keep:
- FlashcardsLock in vocabulary and key terms with spaced repetition.
- Practice questionsAnswer exam-style questions and get instant AI marking.
- Mock exams & past-paper vaultSit full mocks and see exactly how examiners award marks.
- Personalised study planA daily plan built around your exam date and weak areas.
Discrete vs Continuous (quantitative only)
Big idea: Discrete data is counted, so values jump in steps (usually whole numbers).
Continuous data is measured, so values can take any decimal in a range.
| Type | How values behave | Typical examples |
|---|---|---|
| Discrete | Counted values with gaps | Number of students, number of goals, number of books |
| Continuous | Measured values on a scale | Height, mass, time, temperature |
Worked example
Classify each variable as discrete or continuous:
(a) number of siblings,
(b) running time for 100m,
(c) shoe size,
(d) exact age.
Step by step
- Number of siblings is counted in whole numbers only
- Running time is measured and can include decimals
- Shoe size is recorded in fixed steps (e.g., 7, 7.5, 8), so treated as discrete in this context
- Exact age can take any decimal value, so continuous
Final answer
(a) discrete, (b) continuous, (c) discrete (step-based), (d) continuous.
IB exam habit: Ask yourself: was this value counted or measured?
Counted usually means discrete.
Measured usually means continuous.
Study smarter, not longer
Most students waste 40% of study time on topics they already know. Our AI tracks your progress and optimizes every minute.
Classifying data in context
Worked example — classify data
For each piece of data, state whether it is qualitative, discrete quantitative, or continuous quantitative:
(a) Time taken to run 100 m
(b) Number of red balls in a bag
(c) Student opinion on school meals
Solution
- (a) Time taken: Can be any value (19.5 s, 19.57 s, ...). Measured, not counted.
- (b) Red balls: Must be whole number (3 balls, not 3.2). Counted.
- (c) Opinion: Not a number. Categorical (e.g., 'Good', 'Average', 'Poor').
Final answer
(a) Continuous quantitative, (b) Discrete quantitative, (c) Qualitative
In your answer: Always state ALL three: type (quantitative/qualitative) AND if quantitative, add discrete/continuous.
Why data classification matters
Different data types need different methods: Discrete: Use bar charts, mode is meaningful. Continuous: Use histograms, can calculate mean/median/SD. Qualitative: Use frequencies, mode works.
| Data type | Suitable graph | Key statistic |
|---|---|---|
| Discrete quantitative | Bar chart or stem-and-leaf | Mode or median |
| Continuous quantitative | Histogram or frequency polygon | Mean or SD |
| Qualitative | Bar chart or pie chart | Mode |
In Part A (statistics): The IB exam expects you to: (1) identify the data type, (2) choose the right statistical method, (3) justify your choice.