# 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

Unimodal Distribution

Left-Skewed Dataset

Multimodal Dataset

Bimodal Dataset

Uniform Dataset

Right-skewed Dataset

Symmetric Distribution in Histogram

Dataset Outliers

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.

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.

Multimodal Dataset

Multimodal Dataset

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

Bimodal Dataset

Bimodal Dataset

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

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.

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.

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.

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.

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`

.

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.

- 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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