Unit 6 - Lesson 5 - Grade 8: Illustrative Mathematics

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18 Questions

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Grade 8 Unit 6
Lesson 5: Describing Trends in Scatter Plots
CC BY 2021 Illustrative Mathematics®

Instructions

Grade 8 Unit 6
Lesson 5: Describing Trends in Scatter Plots
CC BY 2021 Illustrative Mathematics®

Lesson: Describing Trends in Scatter Plots

Which One Doesn’t Belong: Scatter Plots (Warm Up)

Which one doesn’t belong?

Fitting Lines

Your teacher will give you a piece of pasta and a straightedge.

Here are two copies of the same scatter plot. Experiment with drawing lines to fit the data. Pick the line that you think best fits the data. Compare it with a partner’s.

Here are two copies of another scatter plot. Experiment with drawing lines to fit the data. Pick the line that you think best fits the data. Compare it with a partner’s.

In your own words, describe what makes a line fit a data set well.

Good Fit Bad Fit (Optional)

The scatter plots both show the year and price for the same 17 used cars. However, each scatter plot shows a different model for the relationship between year and price.  

Look at Diagram A.

For how many cars does the model in Diagram A make a good prediction of its price?

For how many cars does the model underestimate the price?

For how many cars does it overestimate the price?

Look at Diagram B.

For how many cars does the model in Diagram B make a good prediction of its price?

For how many cars does the model underestimate the price?

10.

For how many cars does it overestimate the price?

11.

For how many cars does the prediction made by the model in Diagram A differ by more than $3,000? What about the model in Diagram B?

12.

Which model does a better job of predicting the price of a used car from its year?

Practice Fitting Lines

13.

Is this line a good fit for the data? Explain your reasoning.

14.

Draw a line that fits the data better.

15.

Is this line a good fit for the data? Explain your reasoning.

16.

Draw a line that fits the data better.

Cool Down: This is One Way to Do It

This is One Way to Do It

17.

Elena said, “I think this line is a good fit because half of the points are on one side of the line and half of the points are on the other side.” Do you agree? Explain your reasoning.

18.

Noah said, “I think this line is a good fit because it passes through the leftmost point and the rightmost point.” Do you agree? Explain your reasoning.