# Course 4 week 3 quiz non max suppression

in question 6 : if the two cars are separated then the IoU between two bounding boxes will be zero thus smaller than the threshold and should be no elimination of either boxes then why my answer is considered wrong??
mahmoud

Sorry, but there is not enough information in your post to really answer. One thing to note: on a lot of the quizzes, the order of the questions can change, so the question number is not determinative.

There is a question involving bounding boxes and IOU, but the problem people typically have is not to do with the boxes that don’t intersect. There are some other issues with understanding the effect that IOU actually has. Here’s a previous thread which I think is about the same quiz question. Please have a look and let us know if that doesn’t answer your question.

I had a problem with this question too. Here is my answer which I still think is correct (but was marked as incorrect):

Did you read this other thread that was linked from the earlier responses on this thread? You’re right that only one of the two boxes that overlap are included, but the other independent box containing the small white car on the right side of the image is eliminated because its confidence score is 0.26, which is below the 0.4 threshold.

In other words there are two ways to get eliminated here: because the box has a high IOU with another box with a higher confidence or the end result of the IOU elimination is a box below the overall confidence threshold.

Ah, I knew I missed something! Thanks.

Still, the explanation for the correct answer doesn’t look right to me: 0.26 was eliminated not because it was less then maximum but because it didn’t pass the threshold.

Well, they are only talking about the part that they thought might be controversial. But at a higher level, you’re right that it would have been better if they had covered all the issues.