Unit 1 – First-Degree Equations and Inequalities Chapter 2 – Linear Relations and Functions 2.5 – Statistics: Using Scatter Plots

2.5 –Using Scatter Plots In this section we will review how to: –Draw scatter plots –Find and use prediction equations

2.5 –Using Scatter Plots Bivariate data – Data with two variables –speed and calories –distance and time Scatter plot – bivariate data graphed as ordered pairs in a coordinate plane –Positive correlation –Negative correlation –No correlation

2.5 –Using Scatter Plots

The more closely data can be approximated by a line, the stronger the correlation. –Correlations are usually described as strong or weak

2.5 –Using Scatter Plots Line of fit – Finding a line that closely approximates a set of data –An equation of such a line is often called a prediction equation Can be used to predict one of the variables given the other variable

2.5 –Using Scatter Plots Finding a line of fit and predication equation: –Select two points that appear to represent the data well Does NOT have to the data points! –Personal judgment – may be different than others!

2.5 –Using Scatter Plots Example 1 –The table shows the approximate percent of students who sent applications to two colleges in various years since Years Since 1985 Percent

2.5 –Using Scatter Plots Example 1 (cont.) –make a scatter plot of the data and draw a line of fit Years Since 1985 Percent

2.5 –Using Scatter Plots Example 1 (cont.) –Find a prediction equation. What do the slope and y-intercept indicate? –Predict the percent in –How accurate is the prediction?

2.5 –Using Scatter Plots HOMEWORK Page 89 #3 – 6, 12 – 15 all

2.5 –Using Scatter Plots Head Versus Height Help your classmates measure the circumference of each person’s head and his/her height. Record the data into the GoogleDoc. The link can be found on the class wikipage: mathdavis.wikispaces.com

2.5 –Using Scatter Plots Head Versus Height –Graph the data in a scatter plot and write a prediction equation –Explain the meaning of the slope in the prediction equation –Predict the head circumference of a person who is 66 inches tall –Predict the height of an individual whose head circumference in 18 inches