THE MEANT WEIGHT OF A SILVER DOLLAR. J 



II. THE MEAN WEIGHT OF A SILVER DOLLAR. 



In order to test the value of the mean, I have, on ten 

 different days, taken a roll of twenty silver dollars at the 

 bank thus obtaining two hundred single silver dollars as 

 they were in circulation during the first four months of 1901. 



Each coin was separately weighed exactly to the centi- 

 gramme and the mean or average weight was calculated, as 

 well as the so-called probable error of this mean. This 

 probable error we shall explain later on when we shall begin 

 the study thereof; pp. 11-20. 



It will not be necessary here to give the individual weigh- 

 ings except for the heaviest and lightest coin of each series 

 of twenty, that is, the extremes. It is also important to 

 notice the range or difference between these extremes. 



We may here add, that the extremes and range furnish a 

 true indication of the practical concordance of any series 

 of determinations of any single value. We shall see further 

 on, that this is all the probable error can do. 



Determination of the Weight of a Silver Dollar. 



Means, 20 26.72 25.89 0.83 26.39 3-7 



Absol. extremes, 26.77 25.65 1.12 



It will be noticed that the mean weight of the silver dollar 

 in any one roll of twenty coins varies from 26.28 to 26.51 

 grammes or 23 centigrammes ; that is nearly a quartet of a 

 gramme, or almost one per cent of the mean weight of the 

 two hundred single silver dollars weighed. 



