application or intradermal injection of a substance to the skin to test the body's reaction to it. Such a test detects an animal's sensitivity to such allergens as dust and pollen, or to preparations of microorganisms believed to be the cause of a disorder.
A direct relationship graph is a graph where one variable either increases or decreases along with the other. The general equation for a direct relationship graph is y = mx + b, where y denotes the...
b=0, then there is no relationship. The nature of the relationship is discussed as part of correlation. The regression line.  As noted above, a straight line plotted on the Cartesian coordinate system can have the equation y = mx + b. We remember that m is the slope and b is the y-intercept.