Page:Memory (1913).djvu/44

 In the interval, &frac14; P.E. to &frac12; P.E., there occurs a slight piling up of values which is compensated for by a greater lack in the succeeding interval, &frac12; P.E. to P.E. Apart from this, the correspondence between the calculated and the actual results is satisfactory. The symmetry of the distribution leaves something to be desired. The values below the average preponderate a little in number, those above preponderate a little in amount of deviation: only two of the largest eight deviations are below the mean value. The influence of attention referred to above, the fluctuations of which in the separate series show greater deviations toward the upper limit than toward the lower, has not, therefore, been quite compensated by the combination of several series.

The correctness of the observations and the correspondence of their distributions with the one theoretically demanded are greatly improved in the second large series of tests. The latter comprises the results of 84 series of tests taken during the years 1883-84. Each test consisted in memorising six series of 16 syllables each, carried on in each case to the first errorless reproduction. The whole time necessary for this amounted to 1,261 seconds with the probable error of observation of &plusmn; 48.4—i.e., half of all the 84 numbers fell within the limits 1,213-1,309. The exactness of the observations thus had greatly increased as compared with the former series of tests:

The interval included by the probable error amounts to only 7&frac12; per cent of the mean values as against 14 per cent in the earlier tests. In detail the numbers are distributed as follows: