Topic 1: Scatter Plot, Linear Regression and R Value
- Open excel
- In one column enter 8 heights for 10 year old boys (inches) and in the second column enter 8 weights for 10 year old boys (pounds). Ten year old boys height ranges from 42 inches to 62 inches while the weight ranges from 60 to 90 pounds. You can make these up as long as they are reasonable if you do not have access to any data. We want to see if there is a correlation.
- Move your mouse to put a box around the numbers.
- From the insert menu select scatter or the chart that says scatter and then select the chart at the top left on the dropdown
- Click on one of the points
- Select Add Trendline (Note you may need to add Trendline and then click on the line to format Trendline)
- The default radio button is linear, keep it checked
- Check display equation on chart and click on the display r-squared value
- The equation is your least squares line
- On the least squares line the slope is in front of the x value. Also, you can look at the slope of the scatter plot to see if the slope is positive. This will let you know whether to make the r value positive or negative when you take the square root of r^2.
- If the r^2 value is say .0382 then you will click on an excel cell and type
- Note the ^ key is above the 6 key
- This will be your r value and you will make it negative if your slope is negative otherwise leave it positive.
If you have a different version of excel then you may want to search to see how to form a trendline. These instructions work with Office 365 and Office 2010.
Then follow these instructions:
- Attach your excel worksheet with your scatter plot, r value and regression line along with your post if possible. What did you get for your regression line? What was your r value? What did this tell you?
- What would be a scenario where you might need to use this application?
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