Learn on PengienVision, Mathematics, Grade 8Chapter 4: Investigate Bivariate Data

Lesson 1: Construct and Interpret Scatter Plots

In this Grade 8 enVision Mathematics lesson from Chapter 4, students learn how to construct scatter plots by plotting paired data as ordered pairs on a coordinate plane and how to interpret the resulting graphs to identify positive association, negative association, or no association between two data sets. Students also practice recognizing clusters, gaps, and outliers within scatter plots. The lesson builds foundational skills for analyzing bivariate data using real-world contexts such as social media campaigns, sleep and test scores, and basketball statistics.

Section 1

Procedure: Plotting Points on a Scatter Plot

Property

A scatter plot is constructed by converting two-variable data into ordered pairs (x,y)(x, y) where xx represents the first variable and yy represents the second variable, then plotting these points on a coordinate plane with appropriate scales.

Examples

Section 2

Interpreting Scatter Plots: Association

Property

Positive Association: As xx-values increase, yy-values tend to increase (upward trend)

Negative Association: As xx-values increase, yy-values tend to decrease (downward trend)

Section 3

Clustering and outliers

Property

In general, clustering refers to a set of data points that are in close proximity to each other.
Outliers are data points that notably deviate or “stand out” from the general behavior of the data set.
Once outliers have been identified graphically, the researcher must give justification to treat them as outliers in terms of the context.
Outliers are simply data points that “stand apart from the general trend”, regardless of the reason.

Examples

  • On a scatter plot of house prices, most houses in a neighborhood cluster together. A single, very expensive mansion would be an outlier.
  • In a study of test scores versus homework completion, most students form a cluster. A student with zero homework but a perfect score would be an outlier requiring investigation.
  • A plot of animal weights and lifespans shows a cluster for most mammals. A point representing a tortoise, with its long lifespan and moderate weight, would be an outlier compared to the mammals.

Explanation

Clustering is when data points group together, showing a common trend. An outlier is a point that sits far away from this main group. It's crucial to investigate an outlier, as it could be a mistake or a very important, unique piece of data.

Book overview

Jump across lessons in the current chapter without opening the full course modal.

Continue this chapter

Chapter 4: Investigate Bivariate Data

  1. Lesson 1Current

    Lesson 1: Construct and Interpret Scatter Plots

  2. Lesson 2

    Lesson 2: Analyze Linear Associations

  3. Lesson 3

    Lesson 3: Use Linear Models to Make Predictions

  4. Lesson 4

    Lesson 4: Interpret Two-Way Frequency Tables

  5. Lesson 5

    Lesson 5: Interpret Two-Way Relative Frequency Tables

Lesson overview

Expand to review the lesson summary and core properties.

Expand

Section 1

Procedure: Plotting Points on a Scatter Plot

Property

A scatter plot is constructed by converting two-variable data into ordered pairs (x,y)(x, y) where xx represents the first variable and yy represents the second variable, then plotting these points on a coordinate plane with appropriate scales.

Examples

Section 2

Interpreting Scatter Plots: Association

Property

Positive Association: As xx-values increase, yy-values tend to increase (upward trend)

Negative Association: As xx-values increase, yy-values tend to decrease (downward trend)

Section 3

Clustering and outliers

Property

In general, clustering refers to a set of data points that are in close proximity to each other.
Outliers are data points that notably deviate or “stand out” from the general behavior of the data set.
Once outliers have been identified graphically, the researcher must give justification to treat them as outliers in terms of the context.
Outliers are simply data points that “stand apart from the general trend”, regardless of the reason.

Examples

  • On a scatter plot of house prices, most houses in a neighborhood cluster together. A single, very expensive mansion would be an outlier.
  • In a study of test scores versus homework completion, most students form a cluster. A student with zero homework but a perfect score would be an outlier requiring investigation.
  • A plot of animal weights and lifespans shows a cluster for most mammals. A point representing a tortoise, with its long lifespan and moderate weight, would be an outlier compared to the mammals.

Explanation

Clustering is when data points group together, showing a common trend. An outlier is a point that sits far away from this main group. It's crucial to investigate an outlier, as it could be a mistake or a very important, unique piece of data.

Book overview

Jump across lessons in the current chapter without opening the full course modal.

Continue this chapter

Chapter 4: Investigate Bivariate Data

  1. Lesson 1Current

    Lesson 1: Construct and Interpret Scatter Plots

  2. Lesson 2

    Lesson 2: Analyze Linear Associations

  3. Lesson 3

    Lesson 3: Use Linear Models to Make Predictions

  4. Lesson 4

    Lesson 4: Interpret Two-Way Frequency Tables

  5. Lesson 5

    Lesson 5: Interpret Two-Way Relative Frequency Tables