Specific and General Rules
A rule flags one particular rainy route but misses other late deliveries.
Specific and General Rules explained visually
A rule flags one particular rainy route but misses other late deliveries. English captions are optional and start off. The complete transcript follows the written lesson.
What you will learn
A rule flags one particular rainy route but misses other late deliveries.
A practical question
A rule flags only rainy trips on the hill route after five. It catches a few real delays, but misses similar delays on another route. If we remove the hill-route condition, the rule covers more trips. It may also flag many on-time deliveries.
The useful idea
A specific rule covers a narrow set; a more general rule covers a wider one. We need to inspect both the newly caught late trips and the new false alarms. A perfect fit on the few known hill-route examples says little about tomorrow's traffic.
Work through the example
Compare the two rules on held-out deliveries, not merely on the records used to write them. Ask the dispatcher whether a false alarm is costly and whether missing a severe delay is worse. Those decisions determine which trade-off is useful.
Limits and next step
Record coverage and error counts. Next, we'll look at the set of rules still consistent with the examples and what happens when labels conflict.
Worked example
Relax the route condition and compare which additional records the rule now covers.
Quick check: test your understanding
Try it yourself: In the situation described above, explain the method and one reason its output might be misleading.
Check the reasoning
A specific rule covers fewer cases; a general rule covers more and may admit false alarms. More general is not automatically better on future deliveries.
What is the main idea behind specific and general rules?
A specific rule covers fewer cases; a general rule covers more and may admit false alarms.
How is it used in the example?
Relax the route condition and compare which additional records the rule now covers.
What limitation should be checked?
More general is not automatically better on future deliveries.
Further reading
Machine Learning — Tom M. Mitchell.
Original ToolsInVision teaching examples. Editorial approach · Suggest a correction
Accessible referenceLesson 18 transcript151 words · Video transcript · Matches the published narration and captionsOpen transcript
A rule flags only rainy trips on the hill route after five. It catches a few real delays, but misses similar delays on another route. If we remove the hill-route condition, the rule covers more trips. It may also flag many on-time deliveries.
A specific rule covers a narrow set; a more general rule covers a wider one. We need to inspect both the newly caught late trips and the new false alarms. A perfect fit on the few known hill-route examples says little about tomorrow's traffic.
Compare the two rules on held-out deliveries, not merely on the records used to write them. Ask the dispatcher whether a false alarm is costly and whether missing a severe delay is worse. Those decisions determine which trade-off is useful.
Record coverage and error counts. Next, we'll look at the set of rules still consistent with the examples and what happens when labels conflict.