# Describe a Histogram

Learn how to describe a statistical distribution by considering its center, shape, spread, and outliers.

Start## Key Concepts

Review core concepts you need to learn to master this subject

Symmetric Distribution in Histogram

Right-skewed Dataset

Left-Skewed Dataset

Unimodal Distribution

Bimodal Dataset

Multimodal Dataset

Uniform Dataset

Peak of Unimodal Distribution

Symmetric Distribution in Histogram

Symmetric Distribution in Histogram

In a histogram, the distribution of the data is symmetric if it has one prominent peak and equal tails to the left and the right. The Median and the Mean of a symmetric dataset are similar.

Right-skewed Dataset

Right-skewed Dataset

In a histogram, if the prominent peak lies to the left with the tail extending to the right, then it is called a *right-skewed* dataset. In this case, the median is less than the mean of the dataset.

Left-Skewed Dataset

Left-Skewed Dataset

A left-skewed dataset has a long left tail with one prominent peak to the right. The median of this dataset is greater than the mean of this dataset.

Unimodal Distribution

Unimodal Distribution

Modality describes the number of peaks in a dataset. A *unimodal* distribution in a histogram means there is one distinct peak indicating the most frequent value in a histogram.

Bimodal Dataset

Bimodal Dataset

A bimodal dataset has two distinct peaks. This typically happens when the dataset contains two different populations.

Multimodal Dataset

Multimodal Dataset

If a histogram has more than two peaks, then the dataset is referred to as *multimodal*.

Uniform Dataset

Uniform Dataset

A *uniform* dataset does not have any distinct peaks.

As seen in the histogram below, uniform datasets have approximately the same number of values in each group represented by a bar - there is no obvious clustering.

Peak of Unimodal Distribution

Peak of Unimodal Distribution

The center of a dataset is the peak of a unimodal distribution. The statistics that describe the center of a dataset are the mean and median.

Spread of a Dataset

Spread of a Dataset

The spread of a dataset is the dispersion from the dataset’s center. The descriptive statistics that describe the spread are range, variance and standard deviation.

For example, for the dataset `[1, 4, 7, 10]`

, the *range* of the dataset would be the maximum value of the set - the minimum value of the set, or `10`

- `1`

= `9`

.

Dataset Outliers

Dataset Outliers

An *outlier* is a data point that differs significantly from the rest of the values in a dataset.

For example, in the dataset `[1, 2, 3, 4, 100]`

the value `100`

is an outlier because it lies a large distance from the rest of the data.

- 1At this point, you should be familiar with what a histogram displays. If you are not, take a few minutes to complete our lesson on histograms . In this lesson, we’re going to build on those skill…
- 2One of the most common ways to summarize a dataset is to communicate its center. In this lesson, we will use average and median as our measures of centrality. Take the Codecademy lessons on averag…
- 3Once you’ve found the center of your data, you can shift to identifying the extremes of your dataset: the minimum and maximum values. These values, taken with the mean and median, begin to indicate…
- 4Once you have the center and range of your data, you can begin to describe its shape. The skew of a dataset is a description of the data’s symmetry. A dataset with one prominent peak, and similar …
- 5The modality describes the number of peaks in a dataset. Thus far, we have only looked at datasets with one distinct peak, known as
*unimodal*. This is the most common. ![histogram](https://s3.ama… - 6An outlier is a data point that is far away from the rest of the dataset. Ouliers do not have a formal definition, but are easy to determine by looking at histogram. The histogram below shows an ex…
- 7In this lesson, you learned a framework for describing the distribution of a dataset, which includes the following five features: - Center - Spread - Skew - Modality - Outliers If you’re curious,…

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