You would use a scatter plot for the following reasons:

• They are easy to read

• They are easy to make

• They are best when you have fewer than 25 points

• They can be turned into histograms

• They show the following information:

  Clusters — isolated groups of points

  Gaps — large spaces between points

  Outliers — data values that are substantially bigger or smaller

  Variability — how spread the data is

You would use lines on a scatter plot for the following reasons:

• The line divides the plot into two regions by using a 45° line called the y = x line.

• The line distinguishes characteristics between points on, above, or below the line.

• The line can be used to make predictions, especially for algebraic equations of lines, slopes, intercepts, etc.

This is how to make a median fit line:

1. Count the total number of points.

2. Draw two vertical dashed lines so there are approximately the same number of points in each of the three sections. The outer strips should have the same number of points if possible.

3. Find the median point both vertically and horizontally and put a vertical line and a horizontal line at that point, forming an x.

4. Decide whether or not the three x’s lie close to a straight line. Use your ruler to help you decide.

5. Place your ruler so that it connects the two x’s in the outside strips. Now slide the ruler one-third of the way to the middle x and draw the line.

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To make a median fit line on your graphing calculator

• Go to Stat

• Select Calc

• Select Med-med or #3

• Second List1 (using the list you want to use)

• Comma

• Second List2 (using the list you want to use)

• Enter (You’ll get the line information on the screen)

• Go to y= (select the “y” you want to use)

• Go to Vars

• Select Statistics or #5

• Arrow over to EQ

• RegEQ will be highlighted so Enter

• Then hit Graph (make sure your window has been set)