--- title: "Signs: some mistakes cost more" subtitle: "AI robots · Costly mistakes · Lesson 4" --- # Signs: some mistakes cost more **Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}} > **Key question:** A self-driving car that brakes for a plastic bag is annoying. One that drives through a stop sign is dangerous. Its designers make it much more careful about some decisions than others. :::teacher-note **In one sentence:** Students drive a robot with printed signs read by their own model, and make it more careful where a mistake costs more (a higher threshold for Go, and Go twice in a row). **Students should be able to say:** I can explain why some mistakes by a model cost more than others. I can explain how a higher threshold trades speed for safety. I can make a robot act on a costly label only when it is sure. **Width:** the unmarked parts are the floor every student does (predict, run, investigate and make). Typical adds the modify practice; wider adds the real-world contexts. They add contexts, not difficulty. Students work in the online tutorial alongside this sheet. ::: ## Predict :::keep-together **The robot is near the edge of a table. Which mistake by the model is worst?** ☐ Seeing Go when the sign says Stop ☐ Seeing Stop when the sign says Go ☐ Seeing Left when the sign says Right ☐ Seeing Unsure when the sign says Left My prediction, and why: {{lines-3}} ::: :::teacher-note **What happens:** Seeing Go when the sign says Stop: the robot drives off the table. The other mistakes waste time; this one breaks something. So Go should need the most confidence. ::: ## Run Run the program in the tutorial. Was your prediction right? What was different? {{lines-2}} :::typical ## Run Run the program in the tutorial. Was your prediction right? What was different? {{lines-2}} ::: ## Investigate :::keep-together ### Lower **What happens if Go also needed only 70%?** ☐ The robot never moves ☐ The model gets more accurate ☐ The robot moves sooner, but a Stop sign mistaken for Go now and then makes it drive on ☐ Nothing changes ::: :::teacher-note **Answer:** The robot moves sooner, but a Stop sign mistaken for Go now and then makes it drive on A lower threshold sends Go more often, including the times the model is wrong. ::: :::keep-together ### Higher everywhere **What happens if every label needed 95%?** ☐ Nothing changes ☐ It ignores Stop ☐ It drives faster ☐ The robot is very safe but often stops (Unsure) when a sign is clear enough to a person ::: :::teacher-note **Answer:** The robot is very safe but often stops (Unsure) when a sign is clear enough to a person Too much caution everywhere makes a robot that keeps stopping. Caution goes where mistakes are costly. ::: :::keep-together ### Where caution goes **Sort each decision: should it need high confidence or is lower fine?** Groups: High confidence, Lower is fine - A car decides the road ahead is clear: {{field-15}} - A music app guesses which song to play next: {{field-15}} - A robot decides it is safe to drive forward: {{field-15}} - A photo app suggests who might be in a picture, for you to confirm: {{field-15}} ::: :::teacher-note **Answer:** A car decides the road ahead is clear → High confidence; A music app guesses which song to play next → Lower is fine; A robot decides it is safe to drive forward → High confidence; A photo app suggests who might be in a picture, for you to confirm → Lower is fine ::: :::typical ## Modify **Stop at once.** Make **Stop** act the moment it arrives, without waiting for forever: stop, red lights, a beep. **Go twice.** The board repeats each label every second, so "Go twice in a row" means about a second of steady Go. Make the robot wait for that before driving. Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} :::teacher-note **One possible solution.** Other correct programs are fine; check that the program runs and does what the task asks. **Stop at once:** ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/16dd240e18db.png?v=c1b3011f456df072) **Go twice:** ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/a8810f2ebf85.png?v=7e83b8fccc44567f) ::: ::: ## Make Make a **careful sign robot**: **Go** only after hearing it twice in a row, **Left** and **Right** turn, and **anything else** (Stop, Unsure, a word it doesn't know, or two seconds of silence) stops it. Lights: **green** going, **yellow** turning, **red** stopped. Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} :::teacher-note **One possible solution.** Other correct programs are fine; check that the program runs and does what the task asks. ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/aef0dfb1fd15.png?v=f050f579f5f5bb27) ::: ## Exit ticket :::keep-together **Why does Go need a higher threshold than Left?** {{lines-3}} ::: :::teacher-note **Answer:** Mistaking Stop for Go can cause a crash; mistaking Left for Right only wastes time. Costly actions need more confidence. :::