8.FGR.6.2 Use Linear Models to Make Predictions

Scatterplots and Trend Lines

8.FGR.6.2 Use the equation of a linear model to solve problems in the context of bivariate measurement data, interpreting the slope and intercepts.

8.FGR.6.3 Explain the meaning of the predicted slope (rate of change) and the predicted intercept (constant term) of a linear model in the context of the data.

8.FGR.6.4 Use appropriate graphical displays from data distributions involving lines of best fit to draw informal inferences and answer the statistical investigative question posed in an unbiased statistical study. 

Make a prediction!

What will the weight of the shipment be for 7 books?

Multiple Choice

Based on the scatterplot, what is the best prediction of the average number of hours a person spends at work every week, if that person spends an average of 10 hours on recreational activities every week?

• 33 hours
• 85 hours
• 50 hours
• 65 hours

​Find the slope of the trend line the same way as you do for a line

Diff in y's/Diff in X's ​

Rise/Run​

​3.5 - 1.5/13-6 = 2/7

​

​​Slope of Trend Line

​The y intercept is where the Trend Line crosses the y axis.

Same as you did when finding the y intercept of a line.​

Y intercept = 27​

​

​​Y intercept of Trend Line

Multiple Choice

Estimate the y-intercept of the trend line by looking at the graph.

• 2
• 1.8
• 1.2
• 0

Best Fit Line (Linear regression)

• Graph the given data.

• Draw a line that represents the trend of the data.

• Find the slope of two points on the line.

• Find the y-intercept.

• Write the equation.

• Graph the given data.

Multiple Choice

The scatter plot shows the relationship between the number of chapters and the total number of pages for several books.  Use the trend line to predict how many chapters would be in a book with 180 pages. 

• 12 chapters
• 15 chapters
• 18 chapters
• 21 chapters

Multiple Choice

What is the equation of the line of best fit

• y= -2x + 10

• y= 10x+ 2

• y=2x+10

• y= 10

Multiple Choice

What is the equation of the line of best fit?

• y= 2x

• y=3x+7

• y= $$\frac{1}{2}x\ +3$$

• y= $$-\frac{1}{2}x\ -3$$