Time-reversed Analysis
David A. Kenny
December 24, 2013
The Basic Idea
• Redo the analysis but flip or reverse the flow
of time.
• So for a two-wave study, have Time 1
become Time 2 and Time 2 become Time 1.
• See Campbell & Kenny, A Primer on
Regression Artifacts (1999), pp. 158-163 for
details.
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So instead of T1  T2 …
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You have T2  T1 …
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Why?
• If you get essentially the same pattern of
results in the time-reversed analysis, as in
the original analysis, that calls into question
the original analysis.
• For the above figures, if we find that the path
from X to Y is bigger than the path from Y to
X in both the regular and the time-reversed
analysis, we should be suspicious of
analyses.
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A Nonsensical Analysis?
• A time-reversed makes no sense.
• The idea is that if the results from a
nonsense analysis make as much as the
regular analysis, then maybe the regular
analysis does not make sense.
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When to Consider a TimeReversed Analysis?
• Some analysis techniques yield the opposite
results when a time reversed analysis is
performed.
• For example if X is regressed on Y2 – Y1 (i.e.,
change) to yield b, then when X is regressed on
time reversed change or Y1 – Y2, the result is –b.
• A time-reversed analysis is more useful when an
earlier time is used to predict a later time.
• If regression toward the mean is a plausible
explanation of a result, then a time-reversed
analysis might be beneficial.
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An Illustration
Kee, K. S., Qreen, M. F., Mintz, J., &
Brekke, J. S. (2003). Is emotion processing a
predictor of functional outcome in
schizophrenia? Schizophrenia Bulletin, 29,
487-497.
(If you have an illustration, please let me
know.)
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