Lesson 14

Outliers & Means

These materials, when encountered before Algebra 1, Unit 1, Lesson 14 support success in that lesson.

Lesson Narrative

The mathematical purpose of this lesson is for students to determine whether outliers are present in a data set. In previous grades, students were introduced to the meaning of outliers and calculating the mean. In the associated Algebra lesson, students think more carefully about the outlier to investigate their source and how the presence of outliers impacts measures of center in a context. This lesson prepares students to identify outlier values, investigate their source, and determine whether to remove the values from the data. Understanding outliers’ impact on the mean will help students in fully grasping the impact in a specific context. Students reason abstractly and quantitatively (MP2) when they determine if a data point is an outlier and consider the effects of an outlier.

Technology is not required for this lesson, but there are opportunities for students to choose to use statistical technology to quickly compute means. Making technology available allows students to engage in MP5 by providing them access to tools they may wish to use to improve their problem-solving strategies.

Learning Goals

Teacher Facing

  • Discover the effect outliers have on the mean.

Student Facing

  • Let’s explore outliers in data sets

CCSS Standards


Building Towards

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