12 



histogram. The confidence bands were computed for this curve, utilizing Kolmogorov's statis- 

 tic 



CORRELATION BETWEEN WAVE HEIGHTS AND PITCH ANGLES 



The scatter diagram* of Figure 10 shows the pitch angles measured on the CASCO 

 plotted as a function of wave heights. Except for scattered observations, this diagram indi- 

 cates a correlation between pitch angle and wave height which may be approximated by a 

 straight line. The figure also indicates that the most probable combination is that correspon- 

 ding to about 3-deg pitch angle and 5-ft significant wave height. 



< o 



X o 



u> o 

 a o 



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^ 



^ 



















,^ 



^ 







^ 



4 











7 





1 











/ 



, 1 



^ 





i^ 

 /' 



^ 



A 











2 



^ 



^ 



X 



















^ 



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4 6 8 



Significant Wove Height,ft 



10 



12 



Figure 10 - Scatter Diagram of Pitch and Wave Height Data of Figure 4 



A straight line was faired by using pitch angle measurements when ship was headed into the waves; these are 

 indicated by O; ^^ numbers give the number of observations. 



DURATION OF SAMPLE 



An estimation of the period throughout which samples must be taken in order to permit 

 a statistically valid prediction is often necessary. The details of the computation involved 

 for two such methods are given in Appendix 2. 



*A scatter diagram is a method of showing the relationship between two associated variables. In this form the 

 independent variable is placed along the abscissa while the dependent variable is placed along the ordinate. It 

 is obvious that if the relationship between the two variables were perfect, every given value on the abscissa 

 would indicate a value of the ordinate. If there is a direct simple relationship between the variables plotted, the 

 points will tend to fall on some curve, possibly a straight line. 



