XXV] 



Introduction 



xliii 



TABLE XXV (p. 36) 



Value of the probability that the mean of a small sample of n, drawn at random 

 from a population following the normal law, will not exceed (in the algebraic sense) 

 the mean of that population by more than z times the standard deviation of the 

 sample. ("Student": Biometrika, Vol. vi. p. 19.) 



When n is greater than 10, it will be sufficient as a rule to use the approximate 

 result 



v r- 73 fr (n-3)x> 

 P= = e 2 dx (xxxv) 



V27T J-oo 



as a measure of the probability. This may be found from Table II. 



Illustration (i). Experiments of A. R. Cushney and A. R. Peebles on the 

 difference in effect of Dextro-hyoscyamine hydrobromide and Laevo-hyoscyamine 

 hydrobromide*. 



Table XXV shows that for z = 135 : 



P = -99854, 



or the odds are 666 to 1 that leavo- is a better soporific than dextro-hyoscyamine 

 hydrobromide. 



Illustration (ii). Difference in weight of crops of potatoes grown by Dr Voelcker 

 with (i) sulphate of potash and (ii) kainite as artificial manure. 



* Journal of Phyiiology, 1904. 



