What does a histogram primarily illustrate?

A histogram primarily illustrates the frequency of numerical data by representing how often each range of values occurs within a dataset. It is a graphical representation that displays the distribution of continuous quantitative data, where data is divided into "bins" or intervals. The height of each bar in the histogram corresponds to the frequency of data points that fall within that particular range.

By plotting the numerical data in this way, a histogram provides insights into key characteristics such as the central tendency, spread, and overall shape of the data distribution. This enables analysts to identify patterns, trends, and anomalies within the data, such as skewness or the presence of outliers.

In contrast, the other options describe different types of data visualizations or analyses. For example, illustrating the distribution of categorical data requires a bar chart rather than a histogram, showing distinct categories instead of ranges. Exploring the relationship between two continuous variables typically involves a scatterplot, where correlations can be evaluated. Lastly, tracking the trend of data over time is best represented by line charts or time series analysis, focusing on changes across time intervals rather than the frequency of numerical values.