Determine the long-term uncertainty (as a percentage) in the mean wind speed for a proposed wind energy project which has onsite data with a mean wind speed of 7.9 m/s with a standard deviation of 0.5 m/s and a nearby long term historical data set is available with 20 years of data, of which 1 overlap with the data taken at the project site. These two data sets are known to correlate with an R^2 of 0.75.