## Key Concepts

Review core concepts you need to learn to master this subject

### 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

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

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

### Bimodal Dataset

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

### 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

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

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

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.

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

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.

Describe a Histogram
Lesson 1 of 1
1. 1
At 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…
2. 2
One 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…
3. 3
Once 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…
4. 4
Once 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 …
5. 5
The 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://conten…
6. 6
An 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…
7. 7
In 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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