Question

Hi Everyone,

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

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

=.0382^.5

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 scatter plot 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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Answer 1

i have attached both image. followed all instructions given in the question. image 1 has the randomly entered (made up) data of heights and weights in the permissible limits.

Just take the square root of the r^2 value and since both the slopes represented by the lines (height and weight) are positive, u do not need to multiply the square root of r^2 value.

answer to Q.2: What did this tell u?

consider the below points that will not only cover this question, but will also be helpful in anything related to this topic hence:

• The R-squared value R² is always between 0 and 1 inclusive.
• Perfect positive linear association. The points are exactly on the trend line.
  Correlation r = 1; R-squared = 1.00
• Large positive linear association. The points are close to the linear trend line.
  Correlation r = 0.9; R=squared = 0.81.
• Small positive linear association. The points are far from the trend line.
  Correlation r = 0.45; R-squared = 0.2025.
• No association. There is no association between the variables.
  Correlation r = 0.0; R-squared = 0.0.
• Small negative association.
  Correlation r = -0.3. R-squared = 0.09.
• Large negative association.
  Correlation r = -0.95; R-squared = 0.9025
• Perfect negative association.
• Correlation r = -1. R-squared = 1.00.

the scenario where we might use this application: consider a few examples:

• Drinking a glass of red wine per day may decrease your chances of a heart attack.

  Taking one aspirin per day may decrease your chances of stroke or of a heart attack.

  Eating lots of certain kinds of fish may improve your health and make you smarter.

  Driving slower reduces your chances of getting killed in a traffic accident.

  Taller people tend to weigh more.

  Pregnant women that smoke tend to have low birthweight babies.

  Animals with large brains tend to be more intelligent.

  The more you study for an exam, the higher the score you are likely to receive.

• The correlation, denoted by r, measures the amount of linear association between two variables.

Hope this answer solves all your doubts and u find it helpful. all the best!