282 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
subscript 1 indicates the percentage efficiency of the operation, 
subscript 2, the dosage on the basis of tree volume 0) 
subscript 3, the temperature. 
(i<® i). 
subscript 4, the percentage of open space ( 100 
-L s/ 
subscript 5, the dosage on the basis of tree space © 
For example, r i2 is the correlation coefficient between percentage 
of efficiency and dosage 
m 
when the temperatrue and open space is 
allowed to vary. The value of these zero order coefficients are given 
in Table 2. 
Table 2. Correlation Coefficients of Variables Involved in Pear 
Psylla Experiments 
Zero Order 
First Order 
Second Order 
Coefficients 
Coefficients 
Coefficients 
r r2 —.502 ±.074 
ri 2 . 3 —.46/ ±.0/8 
r I2 . 3 4 —.464 ± .078 
it,—.240 ±.093 
ri 2 . 4 —.486 ± .076 
r 1 ,. 24 + .150 ±.097 
ri 4 —-.188 ±.096 
r i,. 2 + .137 ±.098 
ri 4 .2 3 —.138 ±.091 
ri S —.411 ±.083 
r I3 |—.220 ±.095 
it, + .667 ± .055 
ri 4 . 2 —. 124 ± .098 
r2 4 + .164 ±.097 
r l43 .152 ±.097 
r, 4 +. 175 ± .096 
r 2 ,. 4 + .657 ±.057 
r 24 ., + .065±.099 
r 34 . 2 + .089±.099 
It will be noted that these values seem to indicate that the most im¬ 
portant factor involved in the successful application of volatile dust is 
the dosage (ri 2 and r i 5 ). Another important result should also be 
noted: viz, a negative correlation between efficiency and temperature 
(ri 3 ) which would mean that, within the range of temperature involved 
in the experiments—61 to 84 degrees, Fahr.-—increase in temperature 
decreased the control. This is contrary to the results of laboratory 
experiments by other workers who claim that the correlation is positive. 
The examination of the data (omitted because of lack of time) reveals 
the fact that, in most instances the heavier dosages were applied when 
the temperature was low and the correlation coefficient r 23 confirms this, 
indicating that the effect of temperature is masked by the influence of 
dosage. This point will be discussed subsequently under partial corre- 
