core practice · coding problem
Compute precision and recall by hand
Given retrieved doc ids [1,4,2,9] and relevant ids {2,4,7}, compute precision@4 and recall@4.
The mechanism
Precision/recall measure set quality; MRR rewards getting one right answer near the top; nDCG rewards graded relevance discounted by rank. Pick the metric that matches what users feel.
Expected evidence
precision@4 = 0.5 (2 relevant in 4), recall@4 = 2/3.
Try this drill in the practice workspace →
Hints when you need them
- Precision = relevant retrieved / total retrieved.
- Recall = relevant retrieved / total relevant in corpus.
Watch for these mistakes
- Reporting accuracy instead of rank-aware metrics
- Using nDCG without graded relevance labels
- Measuring recall without a fixed cutoff k