CU.Ml'l TAilo.N KLLES. Xlll 



RULES \N DETAIL. 



In casting off places of figures, increase by i the last 

 figure retained when the first left-hand rejected figure is 5 or greater ; 

 otherwise leave it unchanged. 



If the last two figures are rejected 



756827.9 becomes 756830. 

 and o.oo 263 439 becomes o.oo 263 4. 



A MEAN OR AVI K\(,K should always be carried to two unreliable 

 figures. 



A mean is more reliable than the single observation from which 



"inputed (in proportion to \ n. the square root of the number 



of observations). Thus, as the data frequently extend to >nly one 



unreliaMe figure, the mean will often have to be earned two places 



further than the single observation. 



Mri.Tiri.n -ATIMN OK DIVISION-. Ascertain from the object of the 

 work the percentage accuracy desired in the final result ; or, by inspec- 

 tion of the data, find the percentage accuracy of that factor for which 

 this is least, /.<-. for which the deviation-measure or the estimated 



tttj is largest. See Kxample i. ]>au r e xvii. 



In direct multiplication or division retain in every factor, product, 

 and quotient throughout the entire process, and in final results, for an 

 accuracy of about 



One per cent, or worse, four (4) places of' significant figures; 



One-tenth per cent, or worse, five (5) places of significant figures; 

 and so on. 



In the ordinary and the shortened processes of lon-_ r multi- 

 plicat tO carry out tin- partial products one place 



i that \i-ldii t place required in the result under tin- 



above rule. 



at^e xvii. 



. vi.-iniM- .--If the multiplication or division is performed by 

 means of logarithms, the mantissa should contain as many places as 

 are required by the foregoing rules for the direct process; i.e. for about 



One per cent, or worse, use four (4) place tables; 



One-tenth per cent, or worse, use five (5) place tables. 



