A nutritionist collects data from 25 popular breakfast cereals. For each cereal, the number of calories per serving is plotted on the x - axis against the number of milligrams of sodium on the y - axis. The value of r for the resulting scatterplot is 0 point 8 3 How would the value of the correlation coefficient, r , change if sodium was plotted on the x - axis and calories plotted on the y - axis?
Answer
A
The value of r would change to negative 0 point 8 3 .
B
The value of r would increase.
C
The value of r would not change.
D
The value of r could increase or decrease, depending of the strength of the new relationship.
Explanation
Switching the variables on the x- and y-axes does not change the correlation coefficient. Correlation is symmetric: it describes the strength and direction of the linear relationship between the two variables regardless of which one is plotted on which axis. So the value remains 0.83, making “The value of r would not change” correct.
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