punktdiagram

Punktdiagram, also known as a dot plot or dot chart, is a graphical representation of a data set in which each observation is shown by a dot placed along a number line according to its value. It is especially suitable for small to moderate samples and for discrete data, where the exact frequency of each value matters. A dot at value x is placed on the axis for every observation equal to x; if several observations share the same value, their dots are stacked vertically or slightly jittered to reduce overlap when data are continuous.

Construction and variants: Start with a horizontal axis scaled to cover the data range. For each observation, place a dot above its value. In larger or continuous data sets, dots can be jittered or stacked in columns to improve readability. Some versions display grouped data by coloring dots to indicate categories.

Interpretation: Punktdiagramm reveals the distribution shape, central tendency, and spread, and makes it easy to spot outliers, gaps, and multimodality. It provides exact counts for individual values, unlike histograms where binning can obscure precise frequencies. However, dot diagrams can suffer from overplotting with large data sets and may require jittering, which can slightly blur exact values.

Use and context: Common in introductory statistics, data exploration, and teaching, punktdiagramm complements histograms and box plots as a simple, transparent display of data. They are particularly helpful for communicating small data sets to a general audience.