Answer it
P1 a4 phishing accuracy
4 marksYou mark it yourself against the marking points
A school tests a new filter that labels each email as phishing or genuine. It runs the filter on 1000 emails whose true class is already known. The results are shown.
| Actual class | Labelled phishing | Labelled genuine |
|---|---|---|
| Phishing (20 emails) | 5 | 15 |
| Genuine (980 emails) | 10 | 970 |
(a) Calculate the accuracy of the filter. Show your working. [2]
(b) Explain why the accuracy is misleading as a measure of how good this filter is. [2]
[4]