For each boat the absolute length in waterline, displacement, as well as Capsize Screening Formula and Comfort Ratio are included in the Bluewater Surf Value (BWSV).
The length in waterline, displacement, Capsize Screening Formula and Comfort Ratio are converted to z-scores, in turn by determining the mean (μ) and standard deviation (σ) for each. The Bluewater Surf Value (BWSV) of a boat is the mean of these 4 z-scores for same boat (while taking into account the direction (positive or negative) in which each criteria loads on Bluewater Surf Value (BWSV) (the higher the Bluewater Surf Value the more seaworthy the boat).
The z-score tells us how far above or below the mean a boat’s score is on each of the criteria, expressed in units standard deviation (σ). Put differently, the raw scores were in different units in the different criterion. The z-scores are all in the same unit, that is, in standard deviation (σ).
Thus, each z-score and the resulting Bluewater Surf Value (BWSV) for each boat draws on the values of the complete population of the over 8000 boat models included in the calculation. That is, the exact Bluewater Surf Value (BWSV) for a specific boat cannot be calculated without letting it influence all the other BWSV values for all the other boats in the population.
Interpretation:
A higher number indicates a more seaworthy boat. A value of 0.40 or higher is often recommended for offshore sailing. However, there is a more valid and reliable measures – read more.
