---
title: "Pareto charts"
subject: "ICT Project Management"
chapter: 10
key: "semester_7/ict_project_management:pareto-charts"
source: https://www.bctengineer.com/q/semester_7/ict_project_management/pareto-charts
site: BCT Engineering
---

# Pareto charts

ICT Project Management · Chapter 10: Project quality management

- Asked in: year not given
- Video: [What is a Pareto Chart? Master the 80/20 Rule for Smarter Problem Solving](https://www.youtube.com/watch?v=3-BRXZcMOeI) — PM Aspirant
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/ict_project_management/pareto-charts
- Whole chapter: https://www.bctengineer.com/md/semester_7/ict_project_management/chapter-10

## Question

What do you mean by pareto charts?

## Short answer

A Pareto chart is a histogram ordered by frequency of occurrence, showing defects by cause and based on the 80/20 rule: about 80% of problems come from 20% of causes. Construct it by sorting causes descending, drawing bars for frequency and a cumulative percentage line, then focusing on the tallest bars.

## Answer

A **Pareto chart** is a histogram, ordered by frequency of occurrence, that shows how many defects or problems were generated by each identified cause. It is based on the **Pareto principle (80/20 rule)**, named after Vilfredo Pareto and applied to quality by Juran: about 80% of problems come from 20% of causes ("the vital few versus the trivial many"). It is one of the seven basic quality tools.

#### Construction
1. Identify the categories of causes or defects.
2. Collect data for a period.
3. Count the frequency of each and sort in descending order.
4. Calculate percentage and cumulative percentage.
5. Draw bars for each category (left axis: frequency), with a line for cumulative % (right axis).
6. Focus on the tallest bars.

#### Example data (software defects)
| Cause | Defects | % | Cumulative % |
|---|---|---|---|
| Requirement errors | 40 | 40 | 40 |
| Coding errors | 30 | 30 | 70 |
| Design errors | 15 | 15 | 85 |
| Interface issues | 10 | 10 | 95 |
| Others | 5 | 5 | 100 |

```text
Count            Cum %
40 |##             100%
30 |## ##          ___----
20 |## ## ##   ---
10 |## ## ## ##
   +-----------------------
    Req Cod Des Int Oth
```

#### Uses
- Prioritise problems and decide where corrective action brings most benefit.
- Focus limited resources on the vital few causes.
- Compare before and after improvement.
- Communicate priorities to management.

#### Advantages and limits
Simple and visual, but based on past data and shows frequency, not necessarily severity or cost; may need weighting by cost.

**Example:** In the table, fixing requirement and coding errors would remove 70% of defects.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What does the Pareto principle state?
   A. About 80% of problems come from 20% of causes
   B. 80% of causes give 20% of problems
   C. Each cause gives equal problems
   D. All problems have one cause
   Answer: A. The vital few causes produce most of the problems. (Key point: Principle)

2. How is a Pareto chart arranged?
   A. Bars in time order with control limits
   B. Bars sorted in descending frequency with a cumulative percentage line
   C. Bars in alphabetical order
   D. Scatter points with a trend line
   Answer: B. Sorting descending highlights the tallest bars. (Key point: Construction)

3. In the example table, fixing requirement and coding errors removes what share of defects?
   A. 40%
   B. 85%
   C. 70%
   D. 30%
   Answer: C. 40% + 30% = 70% cumulative. (Key point: Example)

## Related in ICT Project Management

- [Control charts](https://www.bctengineer.com/question.md?key=semester_7%2Fict_project_management%3Acontrol-charts) — ICT Project Management, chapter 10