The main goal of lag correction is usually to correctly synchronize two channels.  To determine how much lag time to use, follow these steps:

• Identify a short-duration event (a sudden change) that affects both of the channels in question.
• With either the Overlay command or the Multi-Channel Display command (in the VIEW menu), place both channels on the screen.
• Mark a block that extends from the event on one channel to the same event on the other channel.
• Use the Basic Stats option (ANALYZE menu) to determine the time difference (the block duration can also be read at the top of the Results window).  This value should be used as the lag correction for the delayed channel.

• A much simpler method is available, provided you have selected a block that includes an appropriate event (as described above).  Just click the 'Compute Best-fit Lag Time…' button, and a window opens that requests the maximum search time in seconds; to speed up the search process, enter the smallest value that should encompass the best-fit lag (if you want to delay the channel instead of advancing it in time; enter a negative number of the search time):

  

  You are then asked to select the second channel; when that has been done, the program steps through the possible lag times until it finds the best one, which is displayed as in the right image below.

  

  Note: the progress bar usually does not appear on current LabAnalyst versions.

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