Descriptive statistics

Descriptive statistics organize, summarize, and present observed data using measures, tables, and visualizations without generalizing beyond those data.

Arithmetic mean: The sum of a set of values divided by the number of values. It summarizes a dataset with a single measure of its arithmetic center.
Standard deviation: A measure of dispersion that expresses typical distance from the mean in the data's units. It quantifies how widely observations vary around their arithmetic center.
Inferential statistics: Methods that use sample data to estimate, test, or predict features of a broader population. Unlike descriptive statistics, it supports conclusions extending beyond the observed data.
Measures of central tendency: Statistics that describe a distribution's central or typical value. The mean, median, and mode are standard ways to summarize a dataset's center.
Anscombe's quartet: Four datasets with nearly identical basic statistics but markedly different graphical patterns. It demonstrates why matching summaries alone cannot establish that datasets have similar structure.
Median: The middle value in an ordered dataset, or the mean of the two middle values when the count is even. It describes the center while resisting the influence of extreme values.
Histogram: A graph that groups numerical observations into intervals and displays their frequencies with adjoining bars. Its shape reveals distribution features such as skew and multiple peaks.
Exploratory data analysis: An approach to inspecting and visualizing data to discover patterns, anomalies, and useful hypotheses. It overlaps with descriptive summaries but emphasizes open-ended investigation.
Measures of dispersion: Statistics that describe how spread out values are in a dataset or distribution. They complement measures of center by showing how much observations vary.
Simpson's paradox: A reversal in an association across groups when the groups are combined. Aggregated descriptions can suggest a pattern opposite to the one within subgroups.

Linked from 15 pages