Graphical Skills » Histograms and Kite Graphs

What you'll learn this session

Study time: 30 minutes

How to interpret and construct histograms
Understanding continuous data representation
Creating and analysing kite graphs
Comparing data sets using graphical techniques
Practical applications of these graphs in geographical contexts

Introduction to Histograms and Kite Graphs

Graphs help geographers make sense of data. Histograms and kite graphs are particularly useful for showing distributions and patterns that other graphs can't display as effectively. These tools are essential for analysing climate data, population statistics and many other geographical phenomena.

Key Definitions:

Histogram: A graph that shows the distribution of continuous data using bars of different heights, where the area of each bar represents frequency.
Continuous data: Data that can take any value within a range (like temperature, rainfall, or time).
Kite graph: A specialised graph that shows how data changes over distance or time, often used to display changes along a transect.
Frequency: How often a particular value or range of values occurs in a dataset.

Understanding Histograms

Histograms look similar to bar charts but work differently. In a histogram, the bars touch each other because they represent continuous data where one class ends and another begins with no gaps.

📊 Key Features of Histograms

Unlike bar charts, histograms:

Have no gaps between bars
Show continuous data
Can have bars of different widths
Use area to represent frequency
Have class intervals on the x-axis

💡 When to Use Histograms

Histograms are perfect for showing:

Rainfall distribution throughout the year
Temperature ranges in climate studies
Population age structures
River discharge measurements
Soil particle size distribution

Creating a Histogram

To create a histogram, follow these steps:

Organise your data into class intervals (groups)
Count the frequency for each class
Draw the x-axis (showing class intervals) and y-axis (showing frequency)
Draw bars with heights proportional to the frequencies
Ensure bars touch each other with no gaps

When class intervals are of equal width, the height of each bar directly represents the frequency. However, when class intervals have different widths, you need to adjust the heights to ensure the area of each bar correctly represents the frequency.

Important: Unequal Class Intervals

When class intervals have different widths, you must calculate the frequency density:

Frequency density = Frequency ÷ Class width

The height of each bar should represent the frequency density, not the raw frequency. This ensures the area of each bar correctly represents the frequency.

Interpreting Histograms

When analysing a histogram, look for these patterns:

📈 Normal Distribution

A bell-shaped curve with most values clustering around the middle. Example: Heights of people in a population.

📉 Skewed Distribution

Data clusters more on one side. Positive skew: tail extends right. Negative skew: tail extends left. Example: House prices often show positive skew.

📊 Bimodal Distribution

Two peaks showing two common values. Example: Traffic counts with morning and evening rush hours.

Understanding Kite Graphs

Kite graphs (also called spindle diagrams) are specialised graphs that show how data changes along a line or transect. They're particularly useful in geography for showing how variables change with distance.

🌎 Applications of Kite Graphs

Kite graphs are commonly used to show:

Changes in vegetation along a transect
Beach profiles and sediment size changes
Urban land use changes from CBD to suburbs
Temperature or pollution changes across an area
Species diversity along an environmental gradient

📐 Key Features of Kite Graphs

A kite graph typically has:

A horizontal axis showing distance or location
A vertical axis showing the value or abundance
Shaded areas forming "kite" shapes
Multiple variables that can be compared
Clear patterns of change visible at a glance

Creating a Kite Graph

To create a kite graph, follow these steps:

Draw a horizontal baseline representing your transect or distance
Mark sampling points or distances along this line
For each variable, plot values vertically above and below the baseline
Connect the points to form kite shapes
Shade or colour each kite to distinguish different variables

Case Study: Sand Dune Succession

Kite graphs are perfect for showing plant succession across sand dunes. In a study at Studland Bay, Dorset, researchers created a kite graph showing how different plant species change in abundance as you move inland from the beach. Marram grass dominated the foredunes, while heather became more common in older, more stable dunes further inland. The kite graph clearly showed how each species had its own "peak zone" where conditions were optimal for its growth.

Interpreting Kite Graphs

When analysing a kite graph, look for:

Peak zones: Where a variable reaches its maximum value
Transitions: Where one variable decreases as another increases
Patterns: Gradual or sudden changes along the transect
Relationships: How different variables relate to each other

Practical Applications in Geography

☔ Climate Studies

Histograms are excellent for showing rainfall distribution throughout the year. A histogram of monthly rainfall can reveal whether a climate has distinct wet and dry seasons or more evenly distributed precipitation. For example, a tropical monsoon climate will show a strongly skewed histogram with high rainfall bars during monsoon months.

🏠 Urban Studies

Kite graphs can show how land use changes along a transect from the CBD to rural fringe. The width of each kite shows the percentage of land devoted to different uses (commercial, residential, industrial, etc.) at different distances from the city centre, revealing urban patterns and structure.

Common Mistakes to Avoid

When working with histograms and kite graphs, watch out for these common errors:

Leaving gaps between histogram bars (incorrect for continuous data)
Not adjusting for unequal class intervals in histograms
Forgetting to label axes and include units
Using inappropriate scales that distort the data
Trying to include too many variables on a single kite graph

Exam Tip

In your iGCSE Geography exam, you might be asked to interpret a histogram or kite graph, or to select the most appropriate graph type for a given dataset. Remember that histograms are for continuous data distributions, while kite graphs show how variables change along a transect. Practice drawing and interpreting both types of graphs using real geographical data.

Summary

Histograms and kite graphs are powerful tools in a geographer's toolkit. Histograms help us understand how continuous data is distributed, showing patterns like normal distributions, skews and clusters. Kite graphs excel at showing how variables change along a transect or distance, making them perfect for studying gradual environmental changes.

By mastering these graphical skills, you'll be better equipped to analyse and present geographical data in your coursework and exams. Remember that the choice of graph should always be guided by the type of data you have and the story you want to tell with that data.

🧠 Test Your Knowledge!