then 



^0.025 " ^'^^ 



Op = 0.09 (14) 



The value for o„ represents the approximate sampling error or standard de- 

 viation involved in the estimation of F(x) . In order to state this error 

 in terras of the Y-year significant wave height, it is necessary to define 

 the quantity known as the coefficient of variation or CV . The CV is 

 the standard deviation of a variable divided by the mean of the variable. 

 At the median where F(x) = 0.5 , the CV for the quantity F{x) will be 

 approximately 



CVp = ^ (15) 



CVp = 0.18 (16) 



The CV for F(x) is approximately equal to the CV for F (x) , the cumu- 

 lative probability density for the Y-year significant wave height (Borgman 



1982); thus, if a„ is the standard deviation for F (x) and since F{^(x) 



R ^ 



= 0.37 for the R-year wave, then 



a - 0.37CVp 



" (17) 



= 0.07 



16. The final step in the reliability analysis is to express the error 



in terms of the R-year significant wave height error o . This is accom- 



R 

 plished by means of the approximate formula 



3 



^R ^R 

 where 3 = the slope of Fp evaluated at Xp . The formula for 3 



3F(X„) 



(18) 



^ = uR g^" exp |uR[1 - F(Xp)]| (19) 



18 



