Table 4. Statistical Summary 





Pier 



11 



Pier 



12 



Pier 



13 



Pier 



14 



Variable Statistics 





































NCEL 



FP01 



NCEL 



FP01 



NCEL 



FP01 



NCEL 



FP01 



Sample Size 



30 



117 



30 



147 



30 



183 



30 



205 



Mean Value , in 



12 



12 



12.5 



12.3 



12 



12 



11.9 



11.9 



Standard Deviation, in 



0.9 



1.0 



1.8 



1.5 



1.6 



1.5 



1.0 



1.1 



Coefficient of 



8 



9 



15 



12 



14 



13 



10 



9 



Variation, % 



















Confidence Interval: 



















Upper Limit, in 



12.3 



12.1 



13.0 



12.5 



12.5 



12.2 



12.2 



12.0 



Lower Limit, in 



11.7 



11.8 



11.9 



12.1 



11.5 



11.8 



11.6 



11.8 



Sample Size Require- 



















ment Based Upon 



















Initial Sample 



















90% Confidence 



8 



16 



35 



25 



28 



25 



11 



13 



Level 



















95% Confidence 



13 



16 



50 



35 



40 



35 



16 



19 



Leve] 



















Attribute Statistics 



% of Borer Activity 



38 a 



38 



53 



47 



47 



73 



20 



30 



Standard Error, % 



4.9 



3.8 



9 



3.3 



9 



2.3 



7.3 



2.4 



The attribute data for Pier 11 were obtained from a 

 sample size of 96. 



Except for Pier 12, the sample size of 30 elements was sufficient 

 at the 90-percent confidence level for an accuracy of 0.50 inch to pro- 

 vide estimates of the population parameters. To obtain the measurement 

 statistics, the larger samples that were taken (between 3.9 and 6.8 times 

 the number needed for the specified confidence levels) were not econom- 

 ically worth the reduction in the confidence interval about the mean 

 diameter measurement. 



Table 5 reports the results of the Chi-square "goodness of fit" 

 calculations . Using the assumption that the pile diameters are 

 characterized by the normal distribution, the Chi-square "goodness of 

 fit" statistic was compared with the Chi-square distribution for the 

 corresponding degrees-of-freedom for each pier sample. A confidence 

 interval level of 95 percent was used and corresponds to a 5.0-percent 

 area in the right tail of the Chi-square distribution. 



33 



