False Positive Rate (FPR)
Definition
The proportion of true non-matches (or true negatives) that a classification method declares as matches (or positives). Also called the type I error rate or 1 minus specificity. FPR = FP / (FP + TN).
- Also called
- Type I error rate, 1 minus specificity
- Formula
- FPR = FP / (FP + TN)
- Measures
- True non-matches wrongly declared as matches
- Used in
- Classification methods, steganalysis
Common questions
Why does a low false positive rate alone not prove a detection method is reliable?+
FPR only describes performance on true negatives; a method can have a low FPR while also missing many true positives, so it needs to be read alongside the false negative rate or sensitivity to judge overall reliability.
How is FPR relevant to steganalysis specifically?+
A steganalysis tool with a high false positive rate flags many clean files as containing hidden data, which wastes investigative resources and can undermine confidence in a genuine detection, so tool validation reports this rate explicitly.
Related terms
- Blind Steganalysis
- Detection without prior knowledge of the embedding algorithm. A classifier trained on images with and without payloads generalises across multiple tools.
- Decision Threshold
- The cut-off score above which a classification method declares a positive result. Raising the threshold reduces FPR but increases FNR; lowering it...
- Embedding Rate
- The payload size divided by the carrier capacity, usually expressed as bits per pixel. Detection difficulty decreases sharply at low embedding rates...
- False Negative Rate (FNR)
- The proportion of true matches (or true positives) that a classification method fails to detect, declaring them as non-matches. Also called the...
- Rich Model Steganalysis (SRM)
- A feature-extraction approach that computes hundreds of statistical features from pixel-residual co-occurrence matrices and feeds them to an ensemble classifier such as...
- ROC Curve
- Receiver operating characteristic curve: a plot of sensitivity (y-axis) against FPR (x-axis) as the decision threshold is swept from its most lenient...
- Sensitivity (True Positive Rate)
- The proportion of true matches correctly identified as matches. Sensitivity = TP / (TP + FN) = 1 minus FNR. A method...
- Specificity (True Negative Rate)
- The proportion of true non-matches correctly identified as non-matches. Specificity = TN / (TN + FP) = 1 minus FPR. A method...
- Steganalysis
- The forensic discipline of detecting the presence of hidden data in a carrier file. Steganalysis uses statistical tests (chi-squared, RS analysis, sample...
- Targeted Steganalysis
- Detection methods designed against a specific steganography tool or algorithm. Effective when the tool is known but fails against novel or unknown...
Explained in these topics
- False Positive and False Negative Error Rates
- Steganalysis: Statistical Detection MethodsThe proportion of clean (non-stego) files that a detector incorrectly flags as containing hidden data. High FPR increases investigator workload; it does not by...