The Floating Window Criteria settings are used to define windows of inactivity. These windows of inactivity (also called "non-wear periods") can be flagged and excluded from further analysis within ActiLife. This means that you will have the option in the Data Scoring tool to exclude these "non-wear periods" from your analysis. This is useful if you're trying to analyze periods of real activity rather than periods when the subject did not wear the device. Wear Time Validation is used to:
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Exclude non-wear activity periods from further data analysis (as explained above)
OR
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Simply identify periods when the subject did not meet prescribed activity requirements (i.e., the user was inactive for large amounts of time while wearing the device).
The Floating Window Criteria parameters are explained below.
Valid Activity Floor - The minimum count level per minute to qualify a "valid" activity period. Note that this value is scaled to one minute intervals. For example, if the Valid Activity Floor is set to 240 counts per minute, this implies a floor of 40 counts per epoch for a 10 second epoch file. In this example, each epoch that exceeds 40 activity counts will contribute 10 seconds of wear-time" toward the wear-time sum. Once the sum of the wear-time" exceeds the "Flag After..." length (in minutes), the non-wear period will end and a wear-period will begin.
Use Vector Magnitude - When checked, the Valid Activity Floor applies to the vector magnitude of the 3-axis data collected by the device. If the device does not have 3-axis data available, only the vertical axis is used. When unchecked, only the vertical axis data is used to calculate wear time validation.
Flag as "non-wear" after.... - The minimum total of non-wear time required to score a period as a non-wear period. In the previous example (using 10 second epochs), a minimum of 60 consecutive epochs (assuming the default "Flag as "non-wear" after..." time is 10 minutes) must be encountered in order to score a period as "non-wear" time. This example does not take into account the Drop Time or tolerance which is explained below.
Drop Time (tolerance) - The drop time provides the user with a tolerance window for non-wear periods and allows the user to take into account (i.e., filter out) small spikes in activity which should not be considered valid wear time. In the previous example, setting the drop time to a default of 2 minutes means that a non-wear period may contain up to 12 epochs (not necessarily consecutive) of data greater than 40 counts. A non-wear period will no longer be scored as a non-wear period when the tolerance is exceeded.