Mastering E-Prime: Meaning of all time audit measures.

[David McFarlane]

I worked on getting that little write-up done exactly right for at 
least a week, and after posting it still find things to revise; in 
particular, looking back at the E-Prime Reference Guide, I concede 
that the documention was not quite as vague about "Critical Action" 
as I stated (but I still had to do my own tests in E-Prime to clarify this).

Anyway, I should have closed with a list of references, so here it is:

References:
- E-Prime User's Guide, Chapter 3 & Appendix E.
- E-Prime Reference Guide, section 1.3.1.4 Logging Tab.
- E-Basic online help, topic "Time Audit".

-- David McFarlane, Professional Faultfinder


>When you look at the Logging tab on the properties page of any 
>stimulus object, you will find a host of items available for 
>logging.  Most of these are time audit data.  But what do all these 
>items mean, and what are they good for?  Chapter 3 of the E-Prime 
>User's Guide discusses time auditing to some degree, and the timing 
>diagram at Appendix E provides one way to see the relationships 
>between these items.  As an alternative, here I try to set out, in 
>order, a brief description of these items.
>
>First let us distinguish between timing control *settings* and time 
>audit *measures*.  The following items do not reflect any results 
>formed during the course of a stimulus but simply log the settings 
>provided by the user (e.g., you).  You may choose to have any of 
>these logged just to keep a record of settings active during the experiment:
>- Duration:  To reiterate, this does *not* show the actual duration of
>   the stimulus, only the setting as provided by the user.
>- PreRelease:  Affects the TargetOffsetTime (see below).
>- TimingMode:   Event, Cumulative, or Custom, as set by the user (see
>   the online E-Basic Help).
>- CustomOffsetTime:  In Custom timing mode, overrides the
>   TargetOnsetTime (see the online E-Basic Help).
>- CustomOnsetTime:  In Custom timing mode, overrides the
>   TargetOffsetTime (see the online E-Basic Help).
>
>Now, the raw time audit measures, listed in the order in which 
>events occur during the execution of a stimulus object.  These are 
>all time stamps in milliseconds from the start of the current program run:
>- StartTime:  Time at which E-Prime started executing the stimulus
>   object.
>- TargetOnsetTime:  Scheduled time at which presentation of stimulus was
>   to begin; set automatically from GetNextTargetOnsetTime (see online
>   E-Basic Help).
>- OnsetTime:  Time when E-Prime actually submitted the stimulus data for
>   presentation (e.g., proceeded to copy data to display memory or load
>   sound buffer).  This may not coincide with when the stimulus actually
>   got presented, e.g., if data are submitted in the middle of a display
>   refresh cycle then they may not get presented until the next refresh.
>- ActionTime:  According to the online E-Basic Help, time at which
>   E-Prime completed the "critical action" of the stimulus.  The
>   documentation remains somewhat vague about this -- perhaps "critical
>   action" means copying data to display memory, or loading a sound or
>   video buffer.  In my tests, ActionTime never lags more than 1 ms
>   behind OnsetTime, so it serves practically the same purpose as
>   OnsetTime.
>- TargetOffsetTime:  Scheduled time at which offset actions (e.g.,
>   clean-up, ClearAfter, StopAfter) of stimulus object were to begin,
>   e.g., OnsetTime + Duration - PreRelease (Event timing mode), or
>   TargetOnsetTime + Duration - PreRelease (Cumulative timing mode).
>- OffsetTime:  Time when E-Prime actually began the offset actions of
>   the object.  Actions may not take practical effect until next
>   vertical blank, or until presentation of next stimulus.
>- FinishTime:  Time when E-Prime exited from execution of the
>   stimulus object and proceeded to execute the next section of the
>   program (e.g., next stimulus object or inline code).  Note that
>   *execution* of a stimulus *object* may end before *presentation* of
>   the *stimulus* ends; this is the point of PreRelease (as well as
>   happening as a matter of course with some stimuli such as some
>   sounds).
>
>Finally, a few composite time audit measures derived from the raw 
>measures above and provided for convenience:
>- OnsetDelay = OnsetTime - TargetOnsetTime
>- ActionDelay = ActionTime - OnsetTime
>- OffsetDelay = OffsetTime - TargetOffsetTime
>- DurationError = OffsetTime + PreRelease - OnsetTime - Duration
>
>Note:
>- Time audit measures include the ActionTime that follows upon
>   OnsetTime, but no corresponding item to follow upon OffsetTime.
>- No time audit item for time stamp of vertical blank, although many
>   stimuli do not take full effect until just after a vertical blank.
>
>-- David McFarlane, Professional Faultfinder

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