Approved For Release 2000/08/08
: CIA-RDP96-00789R002200410001-2
Meta-analysis of Forced-Choice Precognition Experiments
The difference across subject populations largely results from the
superiority of studies with selected subjects: Studies using subjects selected
on the basis of prior performance in experiments or pilot tests show larger
effects than studies using unselected subjects. As shown in Table 6, 60%
percent of the studies with selected subjects are significant at the 5% level.
The mean z-score for these studies is 1.41 (sd =
1.36). The magnitude of
effect size is significantly higher for selected subjects studies than for studies
with unselected subjects. The /-test of the difference in mean effect size is
equivalent to a point-biserial correlation of .186.
TABLE
6:
Selected versus Unselected Subjects
Subjects
N studies
StoufferZ
Mean ES<ja
SD
%SIG.05
Selected
7.05
0.055
0.072
60.0%
Unselected
223
4.70
0.012
0.068
21.0%
f246 = 2.97,p = .0015
Does this difference result from less stringent controls in studies with
selected subjects? The answer appears to be “No.” The average quality of
studies with selected subjects is higher than studies using unselected subjects
(/27 =
2.05, p =
.051, 2-tailed).
This result appears to reflect a general
tendency toward increased rigor and more detailed reporting in studies with
selected subjects.
Individual versus Group Testing
Subjects were tested in groups, individually, or through the mail. Studies
in which subjects were tested individually by an experimenter have a
significantly larger mean effect size than studies involving group testing
(Table 7).
The /-test of the difference is equivalent to a point-biserial correlation of
.234, favoring individual testing.
Of the studies with subjects tested
individually, 30.6% are significant at the 5% level.
Psychophysical Research Laboratories
Approved For Release 2000/08/08
: CIA-RDP96-00789R002200410001-2
Approved For Release 2000/08/08
: CIA-RDP96-00789R002200410001-2
Meta-analysis of Forced-Choice Precognition Experiments
The methodological quality of studies with subjects tested individually is
significantly higher than that of studies involving group testing (/143 = 3.5,
p = .001, 2-tailed). This result is consistent with the conjecture that group
experiments are frequently conducted as “targets of opportunity,” and may
often be carried out hastily in an afternoon without the preparation and
planning that goes into a study with individual subjects that may be
conducted over a period of weeks or months.
TABLE
7: Individual versus Group Testing
Test Setting
N studies
StoufferZ
Mean ESdit
SD
%SIG.05
Individual
7.24
0.029
0.074
30.6%
Group
104
1.49
0.005
0.064
18.3%
<200 = 2.40,p = .0085
Thirty-five studies were conducted through the mail.
In these studies,
subjects completed the task at their leisure and mailed their responses to the
investigator. These correspondence studies yield outcomes similar to those
involving individual testing.
The combined z-score
is 3.01, with a mean
effect size of 0.021 (sd =
.079). Ten correspondence studies (28.6%) are
significant at the 5% level.
Eleven studies are unclassifiable with regard to experimental setting.
Feedback
A significant positive relationship exists between the degree of feedback
subjects receive about their performance and precognitive effect size (Table
8).
Subject feedback information is available for 95 studies. These studies
fall into four feedback categories: No feedback, delayed feedback (usually
notification by mail), run-score feedback, and trial-by-trial feedback. We
gave these categories numerical values between 0 and 3. Precognition effect
size correlates .258 with feedback level (103 df,p - .004). Of the 48 studies
Psychophysical Research Laboratories
Approved For Release 2000/08/08
: CIA-RDP96-00789R002200410001-2