Sk/ - (phi quartile skewness) . Is that statistical parameter which is a 

 measure of half the sum of the first and third quartile values less the median 

 and is expressed in phi units to the nearest hundredth with the given value 

 computed from the formula: 



Q U + Q -u 

 Sk^ = -!£ 2 -Md/ 



Md/z£ - (phi median). Is the middlemost member of the distribution curve 

 above which 50 percent of the diameters in the distribution are larger and 

 below which 50 percent of the diameters are smaller and is expressed to the 

 nearest tenth of a phi unit. 



The following table is presented for the conversion of phi units to millimeters: 

 /- f& = log„ diameter (millimeters)/ 



Phi OzO Millimeters Geological Classification 



-2 4.0 



-1 2.0 — 



1.0 



1 0.50 



2 0.25 



3 0.125 



4 0.0625 



5 0.0313 



6 0.0156 



7 0.0078 



8 0.0039 



Granule 



Sand 



Silt 



>8 <0.0039 Clay 



20. Total Subsample Dry Weight (gm.) . Dry weight to the nearest hundreth of a 

 gram . 



21 . Sphericity (avg.) . A measure of the approach of the grain to the form of 

 a sphere and expressed as one of the following: high, medium high, medium, 

 medium low, or low. 



22. Roundness (avg.). A function of the sharpness of the grain edges and 

 recorded as one of the following: very angular, angular, subangular, subrounded, 

 rounded, or well rounded. 



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