Two-Way Frequency Tables
Aligned to S-ID.B.5 — Common Core State Standards for Mathematics.
What this lesson teaches
A two-way table sorts data by two categories. The inside cells are joint frequencies, the row and column totals are marginal frequencies, and a conditional relative frequency divides a cell by its row or column total.
Worked examples
Example 1
Of 50 students, 15 of the 25 girls own a bike. The conditional relative frequency of owning a bike among girls is 15 / 25 = 0.6, or 60%.
Example 2
Among the 25 boys, 20 own a bike: 20/25 = 80%. Comparing 80% to the girls' 60% is the association; comparing 20 to 15 is not.
Example 3
Row percentages and column percentages answer different questions. Decide which one your question needs before you compute.
Practice questions
- In a table, 30 of 80 people are the joint total for adults who walk. Interpret that cell.
- If a row total is 40 and a cell in it is 10, find that conditional relative frequency.
- Explain the difference between a joint frequency and a marginal frequency.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Tablas de Frecuencia de Doble Entrada
Una tabla de doble entrada clasifica datos según dos categorías. Las celdas interiores son frecuencias conjuntas, los totales de fila y columna son frecuencias marginales, y una frecuencia relativa condicional divide una celda entre el total de su fila o columna.
Ejemplo 1: De 50 estudiantes, 15 de las 25 niñas tienen bicicleta. La frecuencia relativa condicional de tener bicicleta entre las niñas es 15 / 25 = 0.6, o 60%.
Ejemplo 2: Entre los 25 niños, 20 tienen bici: 20/25 = 80%. Comparar 80% con el 60% de las niñas es la asociación; comparar 20 con 15 no lo es.
Ejemplo 3: Los porcentajes por fila y por columna responden preguntas distintas. Decide cuál necesita tu pregunta antes de calcular.
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