Definition: Histogram — Psychometric Glossary
A histogram is a bar chart with adjacent bars representing the distribution of a continuous variable. Frequently used in the graphs section of the psychometric test.
- Definition and difference from a bar chart
- Distribution reading techniques
- Histogram analysis exercises for the test
- Interpreting frequencies and classes
What is a histogram?
A histogram is a type of chart that represents the distribution of a continuous variable by grouping data into classes (intervals). Unlike a regular bar chart, histogram bars are adjacent because they represent contiguous intervals.
The height of each bar indicates the frequency (number of observations) in each class. The histogram allows you to quickly visualize the shape of a distribution: symmetric, skewed, bimodal, etc.
Histograms in the psychometric test
Histogram questions in the psychometric test require reading frequencies, calculating proportions, identifying the modal class, or comparing distributions.
The main difficulty is accurate reading of values, especially when the scale is fine. You also need to know how to calculate cumulative percentages and interpret the shape of the distribution.
Frequently asked questions
What is the difference between a histogram and a bar chart?
A histogram represents continuous data with adjacent bars (contiguous intervals), while a bar chart represents distinct categories with separated bars. A histogram shows a distribution; a bar chart compares quantities.
How to identify the modal class of a histogram?
The modal class is the one with the tallest bar, i.e., the highest frequency. It is the interval containing the most observations.
How to calculate a percentage from a histogram?
Divide the frequency of the relevant class by the total of all frequencies (sum of all bars), then multiply by 100. For a cumulative percentage, add frequencies from the classes up to the one you're interested in.
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