Question 2.40

2.40 Stretching a scatterplot

Changing the units of measurement can greatly alter the appearance of a scatterplot. Consider the following data:

x −4 −4 −3 3 4 4
y 0.5 −0.6 −0.5 0.5 0.5 −0.6
  1. Draw x and y axes each extending from −6 to 6. Plot the data on these axes.
  2. Calculate the values of new variables x* = x/10 and y* = 10y, starting from the values of x and y. Plot y* against x* on the same axes using a different plotting symbol. The two plots are very different in appearance.
  3. Find the correlation between x and y. Then find the correlation between x* and y*. How are the two correlations related? Explain why this isn’t surprising.