Outliers and Their Effect
Aligned to S-ID.A.3 — Common Core State Standards for Mathematics.
What this lesson teaches
An outlier is a value far from the rest of the data. Outliers pull the mean toward themselves and inflate the range, while the median stays much more stable.
Worked examples
Example 1
The data 4, 5, 6, 7, 100 has an outlier at 100. Its mean is 122 / 5 = 24.4, far above most values, but its median is the middle value 6, which better represents the data.
Example 2
An outlier can be the most important data point. A sensor reading ten times the others may be the failure you were looking for.
Example 3
Never delete an outlier because it is inconvenient. Report it, and say what you did with it.
Practice questions
- Identify the outlier in 12, 13, 14, 15, 92.
- Does the mean or the median change more when an outlier is added? Explain.
- Find the median of 3, 4, 5, 6, 80.
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
Valores Atípicos y su Efecto
Un valor atípico es un valor lejano al resto de los datos. Los valores atípicos jalan la media hacia ellos e inflan el rango, mientras que la mediana se mantiene mucho más estable.
Ejemplo 1: Los datos 4, 5, 6, 7, 100 tienen un valor atípico en 100. Su media es 122 / 5 = 24.4, muy por encima de la mayoría, pero su mediana es el valor central 6, que representa mejor los datos.
Ejemplo 2: Un valor atípico puede ser el dato más importante. Una lectura diez veces mayor que las otras puede ser justo la falla que buscabas.
Ejemplo 3: Nunca borres un valor atípico por incómodo. Repórtalo y di qué hiciste con él.
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