I've got a question from a colleague about what sort of mean to use in calculating the average of the deviations of actuals from a forecast, which are in percent. The data look(s) like this:
-0.26 -0.21 -0.9 1.56 1.88
For example, the last unit above beat the forecast by 1.88%. My intuition was geometric (based on this question), but I am not sure how to to deal with the negative values.
Edit: I think I've figured it out once I had some more coffee. I think you want to transform the data to (1+percentage). For example, enter +4% as 1.04. Similarly, a percentage of -2% would be .98. Would that be correct?