as defined by equation (18). 



- r- I— (18) 



When this is substituted into equation (17) and when simplifications 

 are made, the final result is given by equation (19). 



V N TT - I V N IT - I 



The value of .^E is obtained from the observation of the waves. 

 Usually it is not equal to the true value of v'^E. Frona the above inequality 

 the bounds within which the true value of .J^ will lie, say, 90% of the 

 time, can be found by multiplying ^fE. by the factors determined from 

 (19) with B equal to 1.65 and N equal to the number of observations. 

 For typical values of N, the results of equation (19) yield the values 

 given in table 3 as entered in the columns marked "theoretical.** 



Table 3 



Confidence values of .^/e 



Lower Value Lower Value Upper Value Upper Value 



N (Safety factor) (Theoretical) (Theoretical) (Safety factor) 



9 0.71 ^/E 0.78 yi: 1.40^1: 1.68 Ve 



m m m m 



16 0.76 yi: 0.82^ 1.28-/E 1.44yE 



m m m ^ m 



25 0.80yE 0.85 v^ 1.21 /E 1.33 ^E 



TCI m vn. m 



50 0.85>/e 0.89yE 1.12yE 1.21^1: 



m m rn m 



lOO 0.89>/e 0.92yE 1.09 v^ 1.12^1: 



m m m m 



200 0.92 yi: 0.94 >/E 1.06^1: 1.09^1: 



m m m m 



16 



