Lesson 14.2 ­ Trend Lines and Predictions November 07, 2016

Lesson 14­2Trend Lines

andPredictions

How can you use a trend line to make a prediction from a scatter plot?

Lesson 14.2 ­ Trend Lines and Predictions November 07, 2016

When ordered pairs are created from a linear equation, those points can be plotted with a line drawn through them to represent the linear equation on a graph.

When a scatterplot is drawn, the points are usually not linear, but if there is an association (positive or negative) visible in the pattern of the points, a line can be sketched through the scatterplot to represent the trend of the scatterplot. This trend line is called a line of best fit.

The line on the graph below best represents all of the points in the scatterplot:

Note: A line of best fit is an approximation, so it's possible that two different people will draw two different lines of the same scatterplot.

Once a line of best fit is drawn, finding the equation of that line is important, as it allows predictions to be made about information beyond the scatterplot.

When drawing a line of best fit:• Try to have just as many points above the line as there are below the line.

• Try to draw the line through as many of the "middle" points as possible.

Copy into your notes:

Lesson 14.2 ­ Trend Lines and Predictions November 07, 2016

Write an equation for the trend line.

Predict how long it would take for someone to run 4.5 miles.

y = 10x

45 minutes

Lesson 14.2 ­ Trend Lines and Predictions November 07, 2016

The scatter plot and trend line show the relationship between the number of chapters and the total number of pages for several books. Write an equation for the trend line. Then predict the number of pages in a book with 15 chapters.

y = 10x

Chapter 15

Trend Lines

150

150 pages

Lesson 14.2 ­ Trend Lines and Predictions November 07, 2016

The scatter plot and trend line show the relationship between the number of customers that enter an electronics store in a day and the number of TVs sold. Write an equation for the trend line.

y = 0.05x

Lesson 14.2 ­ Trend Lines and Predictions November 07, 2016

A line of best fit might look like this...

Mrs. West asked her students to report the number of hours they studied for their Algebra test. The day after the test, she plotted the results on the scatterplot below.

Which of the following equations correctly approximates the line of best fit?

A) y = ­10x + 30 C) y = 10x + 30

B) y = ­10x + 60 D) y = 10x + 60

Lesson 14.2 ­ Trend Lines and Predictions November 07, 2016

An outlier is a data point that is very different from the rest of the data in the set.

PA US EPA US E

Lesson 14.2 ­ Trend Lines and Predictions November 07, 2016

Charlotte recorded the cost of different weights of apples and made a scatter plot of her data. Find the equation of the trend line. Use the equation of the trend line to predict the cost of buying 5 pounds of apples.

What is this called? What does it mean?

y = 2x

$10

Lesson 14.2 ­ Trend Lines and Predictions November 07, 2016

Olivia recorded the price of different weights of several bulk grains. She made a scatter plot of her data. Write an equation for the trend line. Predict the cost of 7 ounces and 50 ounces.

y = 0.08x

$0.56 ; $4.00

Trend Line?

Lesson 14.2 ­ Trend Lines and Predictions November 07, 2016

Write an equation for the trend line.

Predict the number of shots made for 15 shots attempted.

Lesson 14.2 ­ Trend Lines and Predictions November 07, 2016

1) Make a scatterplot and draw the trend line.

2) Write an equation for the trend line.

3) Use the trend line to predict the wind chill at 36 mph and 100 mph.

Pull for trend line.

3)

2)

Lesson 14.2 ­ Trend Lines and Predictions November 07, 2016

Homework Time

14-2

Trend Lines and Predictions