Testing Distributional Dependence in the Becker-DeGroot-Marschak ...

that would confirm an unambiguous success of the detailed instructions to produce an
improvement in subject comprehension (or, at least, an improvement in the subjects’ perception
of their comprehension). A robust ordered logit testing whether viewing the detailed instructions
increased the category of clarity of subject responses to this survey question yields a z-score of
0.85 with a corresponding p-value of 0.394.
The round-by-round BDM data yield compelling evidence that the instruction version
affected the magnitude of their elicitations. As displayed in Figure 3, for 19 of the 20 BDM
rounds (all except the 12 th ) the mean WTP reported for subjects who viewed the detailed
instructions is lower than the corresponding mean for the subjects who viewed the basic
instructions. 30 Since there is no obvious prediction about the direction of any effect of detailed
instructions on the magnitude of the subject responses, Table 9 reports the results of two-tailed
tests of means—looking at each round separately—for the data presented in Figure 3. These tests
show the differences in means across instruction versions are statistically significant at the 10%
level for 8 of the 20 rounds for the set of subjects’ first elicitations and 9 of the 20 rounds for the
set of subjects’ last elicitations.
This pattern of reduced average elicitations for the subjects with detailed instructions is
primarily due to the fact that the subjects with detailed instructions consistently gave
elicitations of $0 more often than their counterparts with basic instructions. Figure 4 plots the
last elicitation for each subject in each round by the type of instructions, showing larger circles
when multiple observations coincide. As can be seen, the range of elicitations remains
approximately the same across the type of instructions. For the subjects with basic instructions
the modal elicitation for is $5 for 7 of the 20 rounds, and for 5 of the rounds $0 and $5 have the
same number of observations among this set of subjects. In contrast, the modal elicitation for
subjects with detailed instructions was uniquely $0 for every one of the 20 rounds.
30 Figure 3 compares the means of the last WTP observations from each round, but the general pattern holds (often
stronger) for the first WTP observations from each round.
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