# Transcript: Different types of graphs and charts hotspot activity

## Bar chart or bar graph

Data types: Categorical and numerical

Example uses: the frequency of different colours of cars sold in one month; the number of visitors to a website for each month of a year.

Bar charts and bar graphs are common ways of visualising data. Each bar represents the value of a certain variable* or category. The bars can be vertical or horizontal, though horizontal bars are more likely to be used for categorical data.

Note that this type of visual is technically called a ‘bar chart’ when the data is categorical and a ‘bar graph’ when the data is numerical, though sometimes the terms are used interchangeably.

*variable: something measurable or observable.

## Histogram

Data type: Numerical

Example uses: the number of samples falling into different size or concentration ranges; the ages of participants in a study.

A histogram, also called a ‘frequency graph’, is a bar graph with special formatting used to represent numerical data. There is no space between the bars, and the labels along the x-axis are consecutive* numbers or number ranges. The height of a bar indicates the frequency of that bar’s numerical value, i.e., how often that value occurs in the data set. Histograms are useful for visualising the shape and range of a dataset.

*consecutive: following each other continuously.

## Pie chart

Data type: Categorical

Example uses: countries of origin for a group of people; the relative abundance of different elements in a rock sample.

A pie chart is used to show values that add up to 100%. Each slice of the pie represents a category, and the size of the slice indicates the percentage value of the category—a large piece of the pie, for example, means a large percentage. Pie charts can make it easy to visually compare the values across different categories of data.

## Line graph

Data type: Numerical

Example uses: the number of bacteria in a culture at different points in time; the price of a stock over the course of a year.

Line graphs are used to show changes in a value over time. These graphs can also have multiple lines for comparison, with each line representing a different set of measurements.

## Scatter plot

Data type: Numerical

Example uses: the height and weight of a group of individuals; level of water pollution and number of fish in different bodies of water.

Scatter plots show the relationship between two variables. Each point on the graph represents a single observation, measurement, or other point of data. Clusters of points or points that appear roughly in a line can provide more information about the data being plotted on the graph.

## Box & whisker plot

Data type: Numerical

Example uses: the spread of student scores on different assessments; the reaction times of participants in a study under different conditions.

Also called a box plot, this type of graph is used to show how sets of numerical data are spread out across different values.

Each set of data is represented by a box with whiskers; the rectangle in the middle is the box, and the lines extending from the box are the whiskers. The box represents the middle 50% of the data, with the median line separating the upper 25% and the lower 25% of the data. The whiskers show the highest and lowest values in the data set.

*median: the middle value in a set of numbers. 