1251 
rest a comparison of the time-values of the several groups does not 
reveal any similarity. 
| TABLE VII 
Observers Groups | Arithm. mean Mean deviation Median 
1 8.90 1.70 8.50 
Ist | 
| r 3.90 0.36 4 
I 
| | 8 1.30 8.50 
2d | | 
r 4.10 | 0.56 4 
M. ( | 
1 10.40 1.32 11 
Ist | 
| r 5.80 1.30 5 
Il 
| | 8.10 1.50 8.50 
2d | 
r 4 0.60 4 
1 5.40 1.40 5.50 
Ist | 
| r 2.60 0.80 2.50 
| | I 3.60 0.68 4 
| og | 
| r 2.30 0.76 2.50 
R. ( 
1 8.20 1.40 7.50 
Ist | 
; | r 3.10 0.74 3 
I 
| 1 7 1.60 1.50 
2d | 
r 3.10 0.74 3 
1 10.62 2.37 10 
Ist | 
| r 5.80 1.16 6 
D EU 
| 1 8.70 1.80 8 
2d | 
r | 4 0.44 4 
The tables VIII and IX illustrate the influence that practice exerts 
upon the number of repetitions and upon the learning-time with I 
and II in the learning- as well as in the repetition-experiments. In 
tabulating the data obtained in the learning- and repetition-experi- 
ments as regards the number of repetitions and the learning-time, 
they have been arranged in the order in which they were acquired 
and have then been split into two equal groups. For every group 
we calculated the arithmetical mean, the mean deviation and the 
median. The figures of table VIII refer to number of repetitions, 
80 
Proceedings Royal Acad. Amsterdam. Vol. XIX. 
