Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A medical research team trains a model to detect a rare disease from lab results. The disease occurs in only 1% of patients. The model predicts 'no disease' for every patient and achieves 99% accuracy. Which metric best reveals that the model is failing to identify actual disease cases?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
Accuracy
Accuracy is 99% here, which hides the model's inability to detect the disease.
B
Distractor review
Precision
Precision is the ratio of true positives to all positive predictions. Since the model never predicts positive, precision is undefined or 0, but recall is the more direct measure of missed positives.
C
Best answer
Recall
Recall (sensitivity) is the ratio of true positives to all actual positives. Here recall is 0%, clearly showing the model fails to identify any disease cases.
D
Distractor review
F1 score
F1 score is the harmonic mean of precision and recall. Since recall is 0, F1 is 0, but recall alone already reveals the failure.
Common exam trap
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Technical deep dive
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Related practice questions
Related AI-900 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
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FAQ
Questions learners often ask
What does this AI-900 question test?
Static NAT maps one inside address to one outside address.
What is the correct answer to this question?
The correct answer is: Recall — Recall (sensitivity) measures the proportion of actual positive cases correctly identified. High accuracy can be misleading when classes are imbalanced. Precision measures correctness of positive predictions, F1 balances precision and recall, and accuracy is high but uninformative.
What should I do if I get this AI-900 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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