| Av. % of difference in favor of | Av. % of difference in favor of | Av. % of difference in favor of | ||||
| Cases | First | Cases | Last | Cases | No tendency | |
| Angier | 7 | 19.1 | 4 | 4.9 | ||
| Baldwin | 4 | 20.5 | 1 | 3.4 | ||
| Bell | 1 | 18.2 | 4 | 6.3 | ||
| Davison | 2 | 31.2 | ||||
| Dunlap | 1 | 11.4 | 1 | 2.2 | ||
| Holt | 10 | 19 | 2 | 6 | ||
| Hylan | 2 | 16 | 5 | 25.4 | 5 | 4.9 |
| Johnston | 2 | 25.2 | 4 | 35.5 | 4 | 4.2 |
| Meakin | 2 | 39.7 | ||||
| Meriam | 1 | 29.6 | 1 | 2.2 | ||
| Miller | 3 | 17.1 | 4 | 5.5 | ||
| Moore | 1 | 11.4 | 1 | 2.2 | ||
| Olmsted | 1 | 15.2 | ||||
| Peterson | 1 | 17 | 1 | 9 | ||
| Rogers | 1 | 10.2 | 1 | 5.6 | ||
| Rouse | 1 | 1.2 | ||||
| Shaw | 6 | 16.7 | 5 | 7 | ||
| Windate | 1 | 11.4 | 1 | 1.2 | ||
| Yerkes | 2 | 42.7 | ||||
a. Relation of the Error to the Absolute Length of the Total Exposure. Table XV is set to answer this question. It is unsatisfactory in that but two observers took part in both XIII and XV. The material used for judgment consisted of the same cards used in the earlier experiment, but presented now in the One-Group Apparatus. The time of exposure was changed from 3/5 sec. to 1/25 sec. for each group. As the space-error was eliminated, the tendency to a time-error, if present at all, would presumably have freer play.
But the difference-values of the new table are for the most part very small. We have thus the further fact about the time-error that, under the conditions studied, it appears to be independent of the absolute length of exposure, when the groups are equal in this respect. To this we may add another fact drawn from Table XIV, that with the One-Group Apparatus the time-error is greater on the whole where the groups are differentiated by other factors. Thirdly, the values for Table XIII show that with all complicating factors withdrawn, except the differences in position, the error is at a maximum. This may be significant of the effect of space-differences upon that error, or, more probably, be due to the general difference between work by daylight and work in a dark room by artificial light. We shall be better able to consider this later.
TABLE XV
- 88 experiments with each of two subjects.
- 176 experiments with one subject.
- 154 experiments with one subject.
- 66 experiments with one subject.
- Exposure = 125 sec.
| First | Last | No tendency | |
| Subjects | 1 | 4 | |
| Av. % of difference in favor of | 15.2 | 6.8 |
3. The Distribution-Error.
The last of our three "errors" of experimentation is now before us. We may recall once more the meaning the term has had for us in these studies. It points to a tendency discovered by the use of those cards where all objective factors were in the course of a series equalized,—a tendency to mass one's judgments in favor of a particular arrangement of the circles; though each group had been constructed with a view to filling the given area as homogeneously as an irregular arrangement would allow.
As in the two "errors" preceding, so here we must get possession of the facts that gave rise to the present enquiry. Table XVI presents them to us, gathered out of all the tables wherein such a tendency has been technically reckoned with. But first a few words of explanation are needed to make the new table intelligible. Two sets of results are found in its two parts. In each set the particular group-arrangements employed and the frequency of their appearance are exactly the same. The two sets differ, as their headings suggest, in that the material for the second set was formed out of the first by replacing the small-difference cards by those having equal groups. Such a change as this might affect the proportion of judgments given in favor of the two sets of arrangements in a particular series, and these new results are, therefore, no longer fully comparable with the earlier ones. In presenting the directions of tendency in the results, it is impossible here, as in all the similar cases throughout the tables, to name a factor as a standard in whose favor all the judgments in the plus column should be understood as given,—impossible for this reason that, because the very method by which the circles were distributed in the groups, the experimenter was unable to satisfy himself as to the significant differences in the arrangements. All the results, however, when analyzed on this basis, were recorded consistently, so that consistencies and agreements among the observers might be readily apparent. We can now understand in part what Table XVI has to say to us.