3. Data Presentation

Graphs & Charts

Graphs

Graphs are pictorial presentations of data. They should be chosen to enable the data to be displayed in the most effective and clear way possible. All diagrams must be fully labelled, and care must be taken to select an appropriate scale so the data is not in any way capable of misrepresentation. All graphs should be accompanied by a sentence or two of explanation.

Bar Charts

A bar chart is a diagram consisting of columns (bars), the heights of which indicate frequencies. A histogram is similar to a bar chart, but without gaps between columns. However, although bar charts can only be used with discrete data (categories such as gender etc.) on the x axis, histograms can use continuous data (measurement of time etc.).

Graph to show what males and females are offering in Lonely-hearts Adverts

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50

Resources Attractiveness

Offering

Freq

uenc

y Males

Females

Pie Chart

A pie chart is particularly suitable for displaying how a population is divided up into different parts and what proportion of the whole each portion represents. The bigger the proportion, the bigger the slice of pie!!

Graph to show who is looking for who in Lonely-Hearts Columns

Women looking for men

Men looking for women

Women looking forwomen

Men looking for men

Line Graph

Line graphs are used to show a trend over time or how a participant’s experiences change. The x-axis on a line graph must always use continuous units of measurement, for example time.

A Histogram can also be used to display continuous data, when the bars are joined with a line, this is known as a frequency polygon.

Graph to show total number of Lonely-Hearts Adverts placed in 2005

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500

1000

1500

2000

Month

Num

ber

Scatter graph

Correlations look for a relationship between two variables. This is not to say that one thing causes another, simply that one thing varies in accordance with another. Correlations are displayed on a scattergraph

Graph to show Age of Male and Age of Female Partner sought

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60

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Male Age

Fem

ale

Age

Normal Distribution

Characteristics of a normal distribution curve, also know as a bell-shaped curve or a Gaussian curve: -

It is bell-shaped It is symmetrical The, mean, median and

mode all fall on the same central point.

The two tails never touch the horizontal axis.

Summary

Bar Chart –Displays frequencies of discrete data

Pie Chart – Displays proportions of the whole population

Line Graph – Displays trends using continuous data

Scattergraph – Displays correlations

Normal Distribution – Expected pattern of many human characteristics such as IQ, height & weight etc.