1380 
years e.g., there are fewer slow workers than among the girls of 
11 years. Boys between 10 and 11 years are about on a par with 
girls of 12. ; 
For the bovs and girls separately and for the two sexes collect- 
ively we have calculated the mean number of mistakes, made by 
the quick, the fairly quick, and the slow workers of each lifetime. 
The arithmetical mean, by the side of it the mean deviation and 
central value is given for each of the three groups and for each 
age in the columns of Table VII. Some figures in the column of 
quick workers under the heading “children” have been put in 
brackets to indicate that they are the results of calculation of the 
data for boys, since among the girls of 8 or 9 years there are no 
quick workers. (See Table VII p. 1379). 
The average number of mistakes invariably increases at each 
age for the boys and girls separately and for both sexes together 
with the speed of working. There is only one exception; for the 
girls of 10 years the mean number of mistakes of the quick workers 
is as great as that of the fairly quick workers. The mean deviation 
is rather high: */,—*/, of the arithmetical mean ; however the central 
value is generally lower than the average. 
In discussing the data of table IV we have already pointed out 
a slowing in the regular progress of the boys between 9 and 10 
years. Among the girls this occurs only between the age of 10 and 
11. This phenomenon is corroborated by the data of table VII. In 
all categories the decrease of the number of mistakes is least for 
boys of 9—10 and for girls of 10—11. As to the quick workers 
among the girls the mean number of mistakes made by girls of 
11 is even greater than that made by girls of 10. 
The above is elucidated by table VIIL which shows for boys and 
for girls the decrease of the number of mistakes from year to year 
in percentages for quick, fairly quick, and slow workers. We also 
added the percentages of the total decrease of the number of mistakes 
in the five years’). The slowing in the decrease of the mistakes of 
boys of 9—10 and girls of 10—11 years, irrespective of their being 
quick, fairly quick or slow workers, is conspicuous. The abrupt 
fall among the boys of 8—9 years is striking, among the girls it 
does not appear before a twelvemonth later. 
The decrease of the number of mistakes in the five years is 
1) Data concerning the total decrease of the number of mistakes in the five 
years for slow workers among the boys and quick workers among the girls have 
not been tabulated here, seeing that there were not enough slow workers among 
the boys of 12 and no quick workers at all among the girls from 8—9 years. 
