In the context of this lesson, is the linear regression slope always positive?
Nope! The slope of a linear regression plot can be positive, negative, 0, or close to infinity.
With linear regression, the line plotted will always be a straight line, and have any valid slope value. However, because it is a straight line, it may not be the best model for certain datasets. For instance, some datasets might form a logarithmic curve, or even strictly have values that fall on either 0 or 1 for every data point. So even though any slope is possible, it is constrained by the linearity.