📊 How statistics help managers
- Identify trends — are sales growing or declining?
- Compare performance — how does this branch compare to another?
- Forecast the future — predict demand based on past data
- Spot problems — unusually high or low figures signal issues
- Support decisions — data-backed arguments are more convincing than gut feelings
Example: A manager sees average customer satisfaction is 4.2/5 but the standard deviation is high. This means some customers love the service while others hate it — inconsistency is the real problem to fix.
⚠️ Limitations of statistics
- Data can be misleading if the sample is too small or biased
- Statistics show WHAT happened, not WHY it happened
- Past data doesn't guarantee future results
- Numbers can be manipulated or cherry-picked to support a preferred conclusion
- Qualitative factors (motivation, culture, reputation) aren't captured by numbers
Statistics are a tool, not the answer. Use them to inform decisions, but also consider context, judgement and qualitative factors! 🧮+🧠
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📊 Constructing Charts and Graphs
The May 2025 exam asked students to DRAW a stacked bar chart (4 marks) and a pie chart (2 marks). You must be able to construct these, not just read them!
Bar charts (simple and stacked)
- Simple bar chart — one bar per category, height shows the value
- Stacked bar chart — bars divided into segments showing subcategories
- Must include: title, labelled x-axis (categories) and y-axis (values/scale)
- Use a ruler and draw to scale
- Include a key/legend if using colours or patterns for different segments
- Bars should be equal width with equal gaps
Stacked bar chart example: A company has 200 employees in 2023 (80 full-time, 70 part-time, 50 temporary) and 250 in 2024 (100 full-time, 90 part-time, 60 temporary). Draw two bars, each divided into three coloured segments. The total height of each bar = total employees for that year.
Pie charts
- Shows proportions of a whole (must add up to 100% or 360 degrees)
- To calculate degrees: (value divided by total) multiplied by 360
- To calculate percentage: (value divided by total) multiplied by 100
- Label each segment with category name AND percentage or value
- Use a protractor for accuracy in exams
- Include a title
Pie chart example: 50 employees — 25 have degrees (50%), 15 have diplomas (30%), 10 have school qualifications (20%). Degrees: 25/50 x 360 = 180 degrees. Diplomas: 15/50 x 360 = 108 degrees. School: 10/50 x 360 = 72 degrees.
Marking criteria checklist
- Fully labelled axes (bar chart) or segments (pie chart)
- Drawn to scale using a ruler or protractor
- Clear title
- Key or legend if multiple categories
- Accurate data plotting
- Not to scale = maximum 3 out of 4 marks
- Missing labels = maximum 2 out of 4 marks