What this guide covers
Selected Sec 1 S1 skills: categorical tables, bar-chart interpretation and misleading presentation. Measures of centre and grouped means are later work.
Categories and counts
A bar chart compares separate categories; a line graph is more suited to ordered changes such as measurements over time. A truncated vertical scale can exaggerate small differences.
Read a category table
In a class survey, 14 students walk, 9 take a bus and 7 travel by car. How many were surveyed, and which display suits a category comparison?
- Total =14+9+7=30 students.
- A bar chart can show three separate travel categories with a labelled count axis.
Check: The three bars should represent counts 14, 9 and 7; their total is 30.
Try it yourself
Work on paper, then compare the steps. These checks do not establish mastery.
A table records 8 students choosing apples, 5 choosing bananas and 7 choosing oranges. What fraction chose bananas?
Total =8+5+7=20. Bananas account for 520=14 of the students. Use the total, not the number of categories, as denominator.
A bar chart compares class counts 96 and 98 but starts its vertical axis at 95. Why might it mislead a reader?
The plotted bar heights above 95 are 1 and 3, which can make 98 appear three times 96. The actual counts differ by only 2; read the numeric scale before judging size.
Where this connects
- Sec 1 data scope →
See tables and displays beside the rest of the level map.
- Next: averages and grouped data →
Sec 2 adds numerical summaries and grouped estimates.
Sources and scope
Original Mentora table and display descriptions aligned to Sec 1 S1 in the MOE G2/G3 Mathematics syllabus. No third-party chart was copied.