1. A. Draw a trend line. It will be easier to write an equation
If you are given a scatterplot, or data that would create a scatterplot (as opposed to a perfectly straight line), you can’t make a perfect linear equation touching all of the points. Instead, you find a __________________________ or a ______________________. You can write an equation of that line. This allows you to estimate approximate values within the data set, or make predictions.
Explorations Workbook Pg 346
The scatter plot shows the relationship between the number of chapters and the
total number of pages for several books. Draw a trend line, write an equation
for the trend line, and describe the meanings of the slope and y-intercept.
A. Draw a trend line. It will be easier to write an equation
for the line if it goes through two of the data points.
Hint: Use (5, 50) as one of the points.
B. Identify another point that the trend line goes through: ( ___ , ___ )
C. What type(s) of association does the scatter plot show?
D. Do you expect the slope of the line to be positive or negative?
E. Find the slope of the trend line. Use
Continued down below!
line of best fit
trend line

2. F. Use the equation , the slope, and the point (5, 50).
Substitute values for y, m and x into the equation and solve for b.
G. Use your slope and y-intercept values to
write an equation in slope-intercept form.
H. What is the meaning of the slope in the situation above?
I. What is the meaning of the y-intercept in the situation above?
1. Use the scatter plot below. Assume the scales on each axis are one unit per tick mark.
Which of the equations would most accurately represent the line of best fit for the data? A. B. C. D.