Statistics Clinic

Statistics carries some of the most reliable marks on the WASSCE Mathematics paper: a table, a graph and two or three readings, every year. It is also where WAEC’s Chief Examiners report the same losses year after year.

The Statistics Clinic fixes those losses one at a time, using what the examiners actually wrote. Every lesson has diagrams, worked answers, practice and a box on what the Chief Examiner reported and how to win those marks back. No magic: just the right habits, practised.

What you’ll be able to do by the end

• Build frequency and cumulative frequency tables without errors
• Find the mean, median, mode, range and standard deviation, for lists and grouped data
• Use class limits, boundaries, widths and midpoints correctly
• Draw histograms, frequency polygons, pie charts and ogives, and read them with evidence
• Find quartiles, percentiles and pass marks from an ogive
• Interpret tables and charts and write conclusions that earn the mark

Statistics in one page

1. Tables and averages

Label every column, check Σf, and divide by Σf for the mean. Use midpoints for grouped data.

2. Cumulative frequency and the ogive

Running totals at upper class boundaries, starting at zero, joined by a smooth curve. Read with dashed lines.

3. Histograms and pie charts

4. Conclusions

The lessons

Practise as you go

Find your weakest skill with the statistics diagnostic test once it goes live, then practise in the Practice Zone. Graph skills are also covered in the Graphs Clinic.

The mistakes examiners see most

Mistake	Fix
cf column copies the frequencies	running total; last cf = Σf
Ogive plotted at midpoints or limits	upper class boundaries, start at zero
Median read with no lines	draw dashed reading lines
Mean ÷ number of classes	÷ Σf
Histogram bars on class limits	class boundaries, no gaps
Calculation but no conclusion	finish with a sentence

Questions learners often ask

Is statistics in every WASSCE Mathematics paper?

Yes. Statistics appears every year, usually in objective questions and at least one theory question.

Which lesson should I start with?

If statistics feels hard, start with Statistics for Beginners; otherwise start with the first lesson in the list and take the diagnostic test.

Where do these examiner comments come from?

From WAEC’s published Chief Examiners’ reports for WASSCE Core (and Elective) Mathematics, listed under sources below.

This clinic is part of How to Pass WASSCE and NOVDEC Core Maths.

Sources and further reading

These lessons are built on what WAEC examiners report year after year, matched to Ghana’s SHS curriculum.

• WAEC Chief Examiner’s Reports: the yearly reports on where candidates lose marks
• NaCCA SHS curriculum: the official Ghana Senior High School curriculum
• Ghana curriculum resources: official teaching and learning resources