Question interpreting output from part 2.

[ZT ZT]

Hello

I have read and reread the documentation, I have also read some posts about this here
but I am still looking for some clarity interpreting some output.

 from "part2_daysummary":

variable name                                                        units
MVPA_E5S_T100_ENMO_0-24hr                       mins            
MVPA_E1M_T100_ENMO_0-24hr                      mins
MVPA_E5M_T100_ENMO_0-24hr                      mins
MVPA_E5S_B1M80%_T100_ENMO_0-24hr        mins? 
MVPA_E5S_B5M80%_T100_ENMO_0-24hr        mins?
MVPA_E5S_B10M80%_T100_ENMO_0-24hr       mins?

I have used bout.metric=4.

So MVPA_E5S_T100_ENMO_0-24hr is Time spent in moderate-to-vigorous based on 5
 second epoch size and an ENMO metric threshold of 100 and
MVPA_E1M_T100_ENMO_0-24hr, and MVPA_E5M_T100_ENMO_0-24hr are similar
but for epochs of 1 and 5 mintues.

MVPA_E5S_B1M80%_T100_ENMO_0-24hr is MVPA calculated based on 5 second epoch setting
bout duration 1 Minute and inclusion criterion of more than 80 percent. 
MVPA_E5S_B5M80%_T100_ENMO_0-24hr are similar but for 5 and 10 min bouts.

So if a subject had values of 15.58, 5, 0, 1.25, 0, and 0 for the six variables respectively,
then they had a total of 15.58 mins of MVPA in the day? and 5 times they had MVPA for between 1 and 5 minutes?
If that is correct why is MVPA_E5S_B1M80%_T100_ENMO_0-24hr = 1.25? Should in not be at least 5?

What if the values were 165.75, 126, 90, 30.83, 14.58, and 14.83?

more info:
  strategy = 1,
  idloc = 1,
  #ndayswindow = 7,
  hrs.del.start = 0,
  hrs.del.end = 0,
  maxdur = 0, 
  includedaycrit = 6,
  qwindow = c(0, 24),
  mvpathreshold = 100, 
  bout.metric = 4,
  closedbout = FALSE, 
  do.imp = TRUE

Thanks
Z

[Vincent van Hees]

All six of time have minutes as unit of measurement.

In order for MVPA_E1M_T100_ENMO_0-24hr to count a minute the average acceleration for that minute needs to meet the threshold. So, even with half of the values above the threshold you can already meet this criteria.

The other metric MVPA_E5S_B1M80%_T100_ENMO_0-24hr can not count on half of the values, it needs at least 80% of the 5 second epochs above the threshold. This would explain the higher value for MVPA_E1M_T100_ENMO_0-24hr.

However, it is theoretically also possible to observe reversed differences. For example, if 80% of the epochs is a fraction above the threshold and 20% of the values is zero. Then the average over the minute may be below the threshold, but the 80% criteria is still met.

Vincent

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