# finding pearson correlation from variable transformation

There's an exercise in our Statistics class:

The produce of crops was measured for 10 years. The standard deviation of produce is 3 tons. The revenue ($y$) from the crops is directly related to the produce via this formula: $y=3x - 2$. Find the value of Pearson correlation between the revenue and crops produce.

I really don't see how this can be calculated from the data. We can calculate the standard deviation of revenue: $$S_{rev} = \sqrt{3^2x^2} = \sqrt{9*9} = 9.$$ The formula for calculating Pearson correlation however requires mean and individual observation values of the variables, which we don't have. Transformations do come into mind but for Pearson correlation transformation we'd need the original Pearson correlation value.

• please add the self-study tag – Antoine Nov 16 '16 at 9:23
• You don't need to know the mean or the individual observation values. You can answer the question directly from the information given – Glen_b Nov 16 '16 at 10:01
• Do you have a hint on how to do this? – Yos Nov 16 '16 at 10:12