Lesson 4 of 8
Test on crates it never saw
Show on a big screenHow good is the board? We test it on kept-back crates. The board never sees them.
Step 1 of 4
- Four crates are on the board. Ten more are kept back.
- Ask the board about each kept-back crate.
- A tick means it matched the seller's word. A cross means it did not.
- 8 ticks out of 10. That is 80% accuracy.
This board is right for 8 of the 10 kept-back crates.
The rule
Test on crates the program never saw. Accuracy is right answers out of all answers.
The kept-back crates are the test data. Accuracy = right ÷ total × 100. Here, 8 ÷ 10 × 100 = 80%.
| Crates on the board | Right, out of 10 | Accuracy |
|---|---|---|
| 2 | 6 | 60% |
| 3 | 8 | 80% |
| 5 | 9 | 90% |
| 7 | 10 | 100% |
In this table, the score never fell as crates were added. Going from 2 to 3 crates gave two more right answers.
Watch out!
A board is right about its own crates. Each one is nearest to itself. So testing on them proves nothing.
Slide to add crates. Watch the accuracy.
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Try the lab to finish this lesson.