Unit 3

Two-Variable Statistics

Unit Narrative

In this unit, students use statistical methods to look for associations in bivariate data. The unit begins with students analyzing categorical data arranged in two-way tables. Students use the relative frequencies of the combinations of those categorical variables to check for evidence of any associations in the data.

The unit then transitions to bivariate numerical data, which are visualized using scatter plots and lines of best fit. Students use technology to compute the lines of best fit and observe how well the linear models match the data. Residuals and correlation...

to access Pre-Unit Assessments.

Section A

Section Goals

Section Narrative

This section focuses on interpreting categorical data using two-way tables. First, students recall from grade 8 how to interpret the values in a two-way table. Then, they expand on their understanding by creating relative frequency tables and use those to look for an association between the variables.

	sunny day	snowy day
sold fewer than 50 cones	27%	64%
sold 50...

Let’s look at categorical data.

Let’s find relative frequencies of categorical data.

Let’s look for relationships between categorical variables.

to access Section Checkpoints.

Section A

Let’s look at categorical data.

Let’s find relative frequencies of categorical data.

Let’s look for relationships between categorical variables.

Section B

Section Goals

Section Narrative

In this section, students focus on linear models and how well they fit data. The first lesson motivates the importance of having a linear model by making sense of the slope and intercept in context and showing how to predict additional values from the model.

The next two lessons are about informally assessing how to obtain the linear models. They...

Let’s explore relationships between two numerical variables.

Let’s find the best linear model for some data.

Let’s examine how close data is to linear models.

to access Section Checkpoints.

Section B

Let’s explore relationships between two numerical variables.

Let’s find the best linear model for some data.

Let’s examine how close data is to linear models.

Section C

Section Goals

Section Narrative

In this section, students look more deeply at the relationships between two variables. In particular, they use the correlation coefficient to categorize the relationships as strong or weak and as positive or negative. They then use their understanding of situations to suggest whether the relationship is causal or merely a correlation.

<p>Graph of a scatter plot, origin O. Horizontal axis labeled r = zero point 8. The data is slightly scattered and trends upward with a positive slope.</p>

<p> </p>

Let’s see how good a linear model is for some data.

Let’s look closer at correlation coefficients.

Let’s get a closer look at related variables.

to access Section Checkpoints.

Section C

Let’s see how good a linear model is for some data.

Let’s look closer at correlation coefficients.

Let’s get a closer look at related variables.

Section D

Section Narrative

In the final section, students have the opportunity to apply their thinking from throughout the unit. As this is a short section followed by an End-of-Unit Assessment, there are no section goals or checkpoint questions.

Let’s collect some data and analyze it.

to access Section Checkpoints.

Section D

Let’s collect some data and analyze it.

to access End-of-Unit Assessments.

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Two-Variable Statistics

Unit Narrative

Section Goals

Section Narrative

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