User`s guide

E-Prime User’s Guide
Appendix A: Timing Test Results
Page A-5
Meaning of Individual Results
Results block
Test ID Test number in the series. Letters indicate multiples of 10.
1% Rule The number of extra trials necessary in order to compensate for the timing errors
that occurred from a less than perfect machine.
Ms Rule Results from the clock testing runs as shown in Figure 2, indicating whether a
greater than ½ millisecond error occurred. A green “+” indicates that the results
suggest the machine can deliver millisecond accuracy (as defined in Chapter 3-
Critical Timing). A red “X” indicates that the test failed to reach the specific
criterion (% Missed Ticks >1% or Maximum Missed Tick > 10ms); therefore, the
computer could produce serious timing or display problems. A yellow “?” indicates
timing concerns (1%> % Missed Ticks > 0.1% or 10ms > Maximum Missed Tick >
5ms).
The status bar moves across the screen as the test proceeds. Ideally, the result
will be all green “+”s. Typically, the first test is poor because the operating system
stabilizes itself after the launch and incremental loading of the test program.
Clock Test
% Extra Trials
Required; Timing Bias
Percentage of extra trials that would need to be run in order to compensate for the
timing errors.
MissTickPercent Percentage of missed millisecond clock ticks. This should be below 0.1%.
Detected Ticks Total number of detected and missed millisecond clock ticks.
Missed Ticks Total number of missed millisecond clock ticks.
Maximum Missed Tick Maximum duration of missed ticks. This value shows, in the worst case, what the
timing error would be during a 10000ms span. This should be small (e.g., less
than or equal to 5ms). Numbers over 10ms should be viewed as a serious timing
problem.
Timing Variance;
Squared Error
Observed timing variance and the measurement error variance (difference
between expected and actual duration variance). If the measurement error
variance is below 1 it is negligible.
Refresh Cycle Test
% Refresh Missed Percentage of refresh cycles that were missed (i.e., percentage of time that the
onset of the vertical blank signal was not detected). This value should be below or
equal to 0.1% (one miss in 1000 refreshes). If the vertical blank simulation code is
enabled (default), then this value should be below or equal to 50%. A miss is
defined as a vertical blanking period that is not between 5 and 20ms at 50Hz to
200Hz (i.e., a miss is considered to have occurred). If the % Refresh Missed is
greater than 0.1% then the Refresh Rate underestimates the refresh rate. If the %
Refresh Missed is above 0.1 % and the very top portion of the screen must be
updated on single refreshes, adjust the screen parameters (i.e., screen resolution,
color depth, refresh rate), or switch to a different video card.
Refresh Missed Count The actual number of times the onset of the refresh cycle was missed.
Refresh Rate Refresh frequency in Hertz (cycles per second).
Refresh Duration Mean time (in milliseconds) between refresh cycles.
Refresh Duration SD Standard deviation (in milliseconds) of the refresh duration.
Refresh Duration Max Maximum duration observed of a single refresh cycle. This should be very close in
value to the Refresh Duration. It is often a multiple of the refresh cycle due to
missing 1, 2 etc. vertical blank signals.
Vertical Blank Duration Mean time (in milliseconds) in which the vertical blank hardware bit was set.
Vertical Blank Min
Duration
Time (in milliseconds) in which the vertical blank hardware bit was set. E-Prime
monitors this bit in order to determine when the refresh cycle begins in order to
synchronize stimulus onsets and to keep the monitor from flashing when updates
are done in the middle of the refresh. E-Prime runs well on Pentium 120 class
machines and above when the vertical blank period is greater than 0.05ms.