2.15:

2.15: Grafico a torta

JoVE Core
Statistics

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JoVE Core Statistics

Pie Chart

2.14: Pareto Chart

14,194 Views

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01:04 min

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April 30, 2023

Overview

A pie chart (or a pie graph) is a circular graphical chart or a pictorial representation of categorical data. It is divided into slices of pie each indicating numerical proportions. It is also used to show the relative sizes of data in a single chart.

In a pie chart, the central angle, the arc length of each slice, and the area are directly proportional to the quantity or percentage it represents. Some real-world examples that can be depicted using pie charts include marks obtained by students in a class, the monthly expenditure of a family, and the cost of construction of a house. With the help of a pie chart, one can easily compare the sum spent on steel, cement, and so on during construction. The actual sum spent on each individual expense can also be computed.

A pie chart's main advantages are that it is simple to use and easy for the audience to quickly analyze and understand information. However, if there is a lot of data, it may become challenging for readers to visualize and assimilate information using a pie chart.

Transcript

Consider a table that summarizes the occurrence of COVID-19 cases in different countries. Such qualitative data with the frequency counts can be represented using the Pie chart, a graph in the form of a circle, just like a pie.

So, how is the data from a table converted into a pie chart?

First, divide the number of COVID cases in country A by the sum of all the COVID cases. Multiply this value by 360 degrees—the degrees in a full circle—to get the sector angle of the corresponding country.

Similarly, calculate the sector angles for the other countries. Using these sector angles, divide the circle into slices equivalent to the given number of categories.

Notice that the percentage frequencies of COVID cases also correspond to the size of their slices. Here, country E, with the largest sector, indicates the highest percentage of COVID cases. In contrast, country F, with the smallest sector angle, shows the least percentage of cases.

Key Terms and definitions

Pie Chart - A circular graphical representation of categorical data and proportions.
Sectors - The individual slices of a pie chart representing specific data.
Central Angle - In pie chart, an angle proportional to the represented data.
Categorical Data - Information that can be categorised into groups; often represented by pie charts.
Relative Frequency - The proportion of the total data value that an individual category represents.

Learning Objectives

Define Pie Chart – Understand its role in data visualization (e.g., pie chart).
Contrast Piechart and Bar Graph– Highlight key differences (e.g., categorical vs quantative data).
Explore Pie Chart Examples – Understand its usage in real-life scenarios (e.g., family expenses).
Explain Central Angle - Its connection to the data portion in a pie chart.
Apply Pie Charts in Context – Methodology for creating pie charts using raw data.

Questions that this video will help you answer

What is a pie chart and how does it represent categorical data?
How is central angle used in the construction of pie charts?
What are the advantages of using pie charts in data visualization?

This video is also useful for

Students – It assists in understanding data analysis and interpretation using pie charts.
Educators – Provides a comprehensive understanding of pie charts for teaching data visualization.
Researchers – Pie charts are vital for representing categorical data in research.
Statistics Enthusiasts – Offers a deeper understanding of data representation and analysis.

Tags

Grafico a torta Grafico circolare Dati categorici Proporzioni Dimensioni relative Angolo centrale Lunghezza dell'arco Area Spesa Costi di costruzione Visualizzazione dei dati Analisi delle informazioni