86 
On the Variations in Personal Equation 
(c) Comparison of Experiments G and D. 
It has been found that in both the Counting and the Estimating Experiments 
there is evidence of a secular change in personal equation, and that in both cases 
the tendency is for the estimates to depart further from the true value of 10 seconds 
in the later series ; in the Counting Seconds there is a decrease, in the Esti- 
mating Seconds an increase in length of estiinate. There is also very little evidence 
of regular sessional change in either experiment. 
EXPERIMENT D. 10 Second Estimating correlation -interval Diagram. 
80 
•70 
, Rk 
R'k e- - 
■60 
50- 
■40 
O -30- 
o 
•20- 
a. 10 
o 
o 
-lO 
-201- 
3 4 5^ 6 7 8 9 10 11 12 IsT 
Interval betv/een successive judgments 
Fig. 20. 
Beyond this the similarity ceases; it is only necessary to compare the values of 
the chief constants (defined on p. 36), 
*S/ R,' 
jCounting "0343 '0338 +'5200 + -0156 
(Estimating -1410 -1785 + -1984 ± -0205 
