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Observed count

As explained in Effective Data Analysis

An observed frequency is the counted or proportional occurrence of a category in the collected data.

An observed count is the number of cases actually recorded in a category. It may also be expressed as that category’s proportion of the collected data, then compared with an expected frequency. section 5.2.3

Use observed counts to:

  • Compare one categorical variable with expected frequencies using a goodness-of-fit test. section 5.2.3
  • Arrange counts for two categorical variables in a contingency table and test their independence. section 5.2.3
  • Identify disproportionality by examining differences between observed and expected values. section 5.2.3

Feature engagement by country

A product analysis counts users who engaged with a feature, broken out by country and experiment group. Comparing these observed counts with expected counts produces a chi-square statistic and highlights cells where engagement differs from expectation. section 5.2.3

Figure 5.11 Comparisons of two categorical variables can be presented as a contingency table, pivoting the results into summarized rows and columns you can easily view.
figure

Use the contingency table to inspect observed counts across categorical rows and columns before comparing them with expectations. section 5.2.3

How Effective Data Analysis covers it

How deep it goes
Defines observed counts and demonstrates their use in contingency tables, chi-square calculations, and difference heatmaps.
Examples
Uses feature engagement counts by country and experiment group, recommendation clicks, expected-count tables, and heatmaps.
What it assumes
Assumes categorical variables and distinguishes recorded frequencies from frequencies predicted under a null hypothesis.
What you can do after
Evaluate categorical patterns by organizing observed counts and comparing them with expected values in a chi-square workflow.
How it connects
Connects observed counts to expected frequencies, contingency tables, chi-square tests, goodness-of-fit tests, and independence tests.

This explainer was generated by Manning's knowledge graph from the text of Effective Data Analysis. The section links point to the parts of the book it draws on.