# SegmentStatistics

**URL:** <https://discourse.slicer.org/t/segmentstatistics/16716>\
**Category:** Support\
**Created:** [March 23, 2021, 12:04pm UTC](https://discourse.slicer.org/t/segmentstatistics/16716 "2021-03-23T12:04:30Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Rachele](https://avatars.discourse-cdn.com/v4/letter/r/a9a28c/32.png) [@Rachele](https://discourse.slicer.org/u/Rachele)\
**Post date:** [March 23, 2021, 12:04pm UTC](https://discourse.slicer.org/t/segmentstatistics/16716/1 "2021-03-23T12:04:31Z")

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Operating system: macOS Big Sur version 11.2.2  
Slicer version: 4.11.20200930

Hi, I’m trying to understand why the number of voxels computed by scalar volume statistics plugin is much different from the number of voxels computed by labelmap statistics plugin. I would like to compute the mean activity inside each VOI, so I need to multiply the mean value by the correspondent number of voxels… which one should I use, scalar or labelmap-computed number?  
If anyone could help me I would be very grateful 😃

 ![Schermata 2021-03-23 alle 12.22.50](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/5/3/5372f5def6a0b065554c3afbdc9c00bef5932caa.png)

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [March 24, 2021, 5:23pm UTC](https://discourse.slicer.org/t/segmentstatistics/16716/2 "2021-03-24T17:23:22Z")

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The difference is most likely due to that the scalar volume plugin only considers that region of the segmentation that overlaps with the chosen scalar volume.