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