Histograms visually demonstrate different distribution shapes. A symmetrical distribution features balanced mirror-image halves. A negatively skewed distribution has its peak toward the upper end with a long negative tail, while a positively skewed distribution peaks toward the lower end with a long positive tail.

Examples of Symmetrical and Skewed Distributions

A researcher creates a histogram to visualize the distribution of reaction times in a psychology experiment. To describe the distinct shape of this distribution, which visual features should the researcher primarily focus on?

When a quantitative variable's distribution is visualized using a histogram, it exhibits a distinct shape. This shape can be described by its peaks and whether the tails are symmetrical or asymmetrical.

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A histogram is a graphical tool used during preliminary analyses to evaluate the distribution and shape of a single variable. By plotting the frequency of different scores, researchers can visually assess key characteristics of the data—such as whether the distribution is unimodal or skewed—which helps them understand what their descriptive statistics represent in real-world terms.

Histogram

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KPU Research Methods in Psychology - 4th American Edition

When constructing a histogram, the spacing between the vertical bars depends on the type of variable being graphed. For a quantitative variable, the bars are typically drawn adjacent to one another with no gaps between them. However, when the variable is categorical, a small gap is conventionally left between the bars to distinguish the discrete categories.

Histogram Bar Gaps

A histogram can be used to display the distribution of self-esteem scores, providing a visual representation of a frequency table. In this histogram, the $$x$$-axis represents the self-esteem variable and the $$y$$-axis represents the frequency. Because self-esteem scores represent a quantitative variable, there are generally no gaps between the vertical bars. However, if a specific score has a frequency of zero—such as having no individuals with a score of $$17$$ in the data set—a noticeable gap will appear at that specific level on the histogram.

Histogram of Self-Esteem Scores

Shape of a Distribution

Which graphical tool is used during preliminary analyses to plot the frequency of different scores and evaluate the distribution and shape of a single variable?

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