8. Explain why it is not of any concern that the least squares line has a negati

Question

8. Explain why it is not of any concern that the least squares line has a negative value for the intercept.

DATA FILE HERE: https://expirebox.com/download/12b419270d0365657d8559cc5c29c7dc.html

MORE INFO:

Fat deposits in the trunk of the body may be more closely linked with bad health outcomes than fat in general.   It can be hard to measure deep abdominal adipose tissue directly.

Despres et al. proposed that waist circumference might be a good predictor variable for deep abdominal adipose tissue. (We’ll see, over the course of our work with these data, that there is an association between these variables, but that we cannot predict precisely enough to use waist circumference as a good measure of an individual’s deep abdominal fat.)

In this dataset, the individuals received CT scans and the area of deep abdominal adipose tissue was measured. Even this isn’t perfect, as it’s an area, the units are cm 2   , and not a volume!

The outcome variable is the area of deep abdominal adipose tissue from the CT scan, the explanatory variable is the individual’s waist circumference in cm.

Explanation / Answer

It is not a concern even if the value of the intercept is negative since this is a valid equation.

It may be the case that at x = 0 , the value may be negative and will increase accordingly.

Also, the equation is made for mathematical justification and not practicallity. Practically , a waist size (x = 0) will not exist . Waist size may start from a positive value (say x = 100) which may give an overall positive value of y.

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