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.

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

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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