chi-square test, although it does not provide estimates of 

 the parameters of the distribution, does provide a good in- 

 dication of the "fit" of the sample distribution to the theo- 

 retical distribution. The chi-square method can be used 

 to give an independent check on the method of moments. 



RECOMMENDATIONS 



1. Use the method of moments described here if 

 better accuracy than that given by overlays is desired to 

 estimate the moments and to determine whether a sample 

 is gaussian or non-gaussian. 



2. In the probability density analysis of a noise sample, 

 use a range of amplitudes covering at least ±4 standard 

 deviations; otherwise large errors in the estimates of the 

 moments will frequently result. 



3. In future applications of the PDA, have the output 

 of the PDA in a digital form rather than a continuous curve, 

 so that the data will be in a form more suitable for the 

 calculation of the moments of distribution. 



38 



