Because it’s impossible to always exactly predict wind speed before it happens, the researchers felt a prediction method was needed that also included a prescribed confidence level, a percentage that demonstrated the likelihood that the wind would be at a specific speed at a certain point of time. In an article in IEEE Transactions on Power Systems, they detail developing a prediction interval which includes a lower and upper bound that not only provides a range of target values within the two bounds, but also provides an indication of their accuracies.