Why some papers write false positive rate per case instead of percentage rate? In some published works, especially in medical image analysis, instead of writing FP rate as percentage, they write it per case, for example, FP: 128.52 [/case].
What is the meaning of this? Is it different from percentage rate? How to calculate it per case?
In general a false positive rate is abbreviated FPR, so it's likely that "FP: 128.52 [/case]." is not the rate but simply the number of false positive instances. In this case they should also mention the total number of instances by case, and you can easily obtain the rate: FPR = FP/total