# Quiz question 6

Hello,

Can someone explain me the right answer for the 6th question of this quiz ?
(The one with the number of boxes remaining after non-max suppression)

First I discard all boxes with probability < 0.4, I remove 1 box (the 0.26 car), then
I take the box with max probability (0.94 pedestrian), check IOU, and keep this box (no intersection nor union) ==> 1 box
I take the next box with max probability (0.74 tree), check IOU, seems < 0.5, so remove that box.
Next : 0.73 car, IOU > 0.5 with 0.62 car, keep 0.73 car and remove 0.62 car ==> 2 boxes
Next : 0.58 motorcycle, no intersection nor union, keep that box ==> 3 boxes
Next 0.48 tree, no more intersection nor union (0.74 tree has been removed), keep that box ==> 4 boxes.

This is not the right answer but I don’t understand why.

Thanks

The IoU threshold means that when 2 boxes have value of IoU > 0.5, then you need to remove them.
When you have IoU < 0.5, it means that the 2 boxes have lesser intersection area, hence we assume them as 2 different boxes. So, it will be 5 boxes in all