Lesson 2-5: Scatter Plots

Lesson 2-5: Scatter Plots

Algebra 2

Read from the textbook and complete the definitions and example. You will need to have your notes approved before you can pick up your homework: 2-5 Worksheet.

Pgs. 81 & 82:

Define:

Scatter Plot: ______

Ex. 1: Housing

The table below shows the median selling price of new, privately-owned, one-family houses for some recent years. make a scatter plot of the data.

Year / 1990 / 1992 / 1994 / 1996 / 1998 / 2000
Price ($1000) / 122.9 / 121.5 / 130.0 / 140.0 / 152.5 / 169.0

Graph the data as ordered pairs, with the number of years since 1990 on the horizontal axis and the price on the vertical axis.

Median House Prices

**Don’t forget your labels . . .

Define:

Line of Best Fit: ______

Prediction Equation: ______

Ex. 2:

Draw a line of fit for the data. How well does the line fit the data?

Find a prediction equation. What do the slope and y-intercept indicate?

Predict the median price in 2010.

Your Turn: Complete these on your own. Base your work off the textbook example.

Example 3A:

The table below shows the approximate percent of students who sent applications to two colleges in various years since 1985. Make a scatter plot of the data.

Example 4A:

The table below shows the approximate percent of drivers who wear seat belts in various years since 1994. Make
a scatter plot of the data.

Example 3B:

Use the information provided in the third example.

** Draw a line of best fit (you may use the above graph so you do not need to graph the stats again)

**Find a prediction equation (Not everyone will have the exact same prediction equation. Based off the points you chose to use for your line of best fit, the slope and y-intercept may vary. That is OKAY. )

For instance, using the points (3, 18) and (15, 13) I can find the slope and y-intercept.

To find the slope:

m = y2 – y1 = 13 – 18 = -5 ≈ -0.42

x2 – x1 15 – 3 12

To find the y-intercept:

y = mx + b Use the point (3, 18): 18 = -0.42 (3) + b

18 = -1.26 + b

19.26 = b

The y-intercept is (0, 19.26)

Prediction Equation: y = -.042x + 19.26

**What does the slope indicate is happening over the years???

**What is the significance of the y-intercept????

**Predict the percent of students who sent in applications to a 2-year college in 2010.

The year 2010 is 25 years after 1985 . . . . so use the prediction equation to find the

value of y when x = 25.

y = -0.42(25) + 19.26

y = 8.76What does that mean??? The model predicts that the percent in 2010 should be around 9%.

Example 4B:

Use the information provided in the fourth example.

** Draw a line of best fit (you may use the above graph so you do not need to graph the stats again)

Slope:

y-intercept:

Prediction Equation:

What does the slope mean????What does the y-intercept mean???

**Predict the percent of drivers who will be wearing seat belts in 2005.