Negative RT Data in E-Prime 1.2

[Michiel Sovijarvi-Spape]

Hi KC and list,
I am not aware of a known bug in E-Prime, especially mighty stable 1.2, that
could cause this. A general, "internal error" seems unlikely to answer the
question, so the way to go about it would be to A) replicate the error, and
B) find out what is responsible for the observation - what part of the bug.
In general then, the task would be to find out how the observed variable is
related to actual performance, and either shift them or, as you say, filter
them.
Scenario one: there's something going on due to incorrect usage of preload. 
Scenario two: there's incorrect calculation of your reading time. For
instance:
An instruction screen is shown, the "reading screen" is shown, which has
60000 ms maximum, but a response terminates screen ("after you're done
reading, press space bar"). Reading time is calculated as "ReadingTime =
ReadingScreen.RTTime - InstructionScreen.OffsetTime". Now, that would
normally work, but imagine a person is a very slow reader (a minute passes):
RTTime is never changed to 0, ergo, 0-8062316=-8062316. 

Anyway, my point really is, add some debugging (debug.print) to find out the
exact relationship between your variable coding and what is going on. Then,
make a decision if you can really be sure you can just filter negative
times.
Cheers,
Michiel


-----Original Message-----
From: e-prime at googlegroups.com [mailto:e-prime at googlegroups.com] On Behalf
Of KC
Sent: 30 May 2012 16:43
To: E-Prime
Subject: Negative RT Data in E-Prime 1.2

I feel I should preface this message by saying that I am not an E- Prime
expert. I've recently begun working on some data generated in an experiment
run using E-Prime 1.2. The data was part of an experiment run by another
student who has since left our lab. I'm cleaning (filtering outliers) the
raw Reading Time data right now and I'm seeing a lot of negative values. Why
is this? Some forums have suggested that it is an internal error of the
program and that the solution is to update to a more recent version of
E-Prime, however, I cannot re-run the experiment. In terms of analysis, how
are these values normally dealt with? Any ideas?

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