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GeoGebraGeoGebra Classroom

Scatter plot and best fit line

Task

Create a Scatter Plot and conduct a Two Variable Regression Analysis for a given data set to explore how outliers affect the best fit line.

Explore the construction...

Instructions

1.In the Spreadsheet View, enter the following data values into the cells of column A: A1:      1         A2:      5         A3:      2         A4:      8         A5:      -2
Hint: Always evaluate your input by hitting the Enter key.
2.Enter the following numbers into the spreadsheet cells of column B: B1:      -1       B2:      2         B3:      3         B4:      4         B5:      1
3.Toolbar Image Create a Scatter Plot from this data: Highlight all cells of columns A and B that contain data. Then, select the tool List of Points from the Spreadsheet View Toolbar and click Create to create points from your data set.
Note: The values in column A determine the x-coordinates and the values in column B specify the y-coordinates of the plotted points.
Toolbar ImageHint: You might want to use the Move Graphics View tool if not all five points are visible in the  Graphics View.
4.Toolbar ImageSelect the Best Fit Line tool from the Graphics View Toolbar. Create the line that best fits your data points by using a selection rectangle that contains all data points plotted.
Hint: Create a selection rectangle by clicking in the upper left corner of the Graphics View and dragging down to the lower right corner of the  Graphics View. Make sure that all data points lie within the selection rectangle.
5.Toolbar ImageExploration: Using this construction you can easily demonstrate how outliers affect the best fit line of a data set. Select the Move tool and drag one of the points to create an outlier.
Hint: You can also change the initial data directly in the  Spreadsheet View.

Try it yourself...