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AI and You 9-12 / Week 03 / Thursday
4/6
Week 03 Β· How Models Learn

Thursday

When data goes stale
// The crew trains Tiny Text by hand to see how training data becomes predictions
⏱ about 20 min

Thursday: When Data Goes Stale

Librarian Joss tapes a new sign to the library door: "Now opening at nine." The crew stops in the hallway to read it.

Comet pulls out the Tiny Text tally table. "Uh oh. Our model still says the library opens at eight."

Wren checks the tallies. "What does the evidence say? Nothing in our cards has changed. The model only knows its training data."

"So we just add two new cards," Comet says, already writing.

Nova projects the old cards and the new ones side by side. "Would you like a hint?" she asks. "Count again. Then ask what happens to the old cards."

Wren turns to you. "Reviewer, how do we fix Tiny Text the right way?"

Stale data

Training data can go stale. It can fall out of date for the place where a system is used.

AI systems may be trained on data that changes over time. That can change how well they work in ways that are hard to understand.

So AI systems may need fixing more often than ordinary software.

Tiny Text was trained when the library opened at eight. The world changed, but its training data did not.

Two ways to retrain

Comet's first fix adds two new cards, both saying "the library opens at nine," and keeps the old ones.

Wren's fix swaps T1 and T5, the two old library-hours cards, for the two new cards.

VersionAfter "at" (tally)Row totalMost likely after "at"
Original Tiny Texteight 2, nine 1, seven 14eight
Comet's fix: add two new cards, keep T1 and T5eight 2, nine 3, seven 16nine
Wren's fix: swap T1 and T5 for the two new cardsnine 3, seven 14nine
COMPARE THE FIXES
  • Read the question.
  • Tap your answer.
In Comet's fix, how many times does "nine" follow "at"?
In Comet's fix, can Tiny Text still say "eight"?
In Wren's fix, how many times does "eight" follow "at"?
Which fix stops Tiny Text from giving the old library hours?

Training changes behavior

AI systems depend on their training data, which is often huge and complex.

Changes made during training, on purpose or by accident, can change how a system performs.

Swapping two cards changed what Tiny Text says. A real system has far more data, so a change can be much harder to trace.

Tiny Text also looks only one word back. So after "at," it cannot tell the library from the gym.

StatementTrue or false?
Training data can go stale.?
Once a model is trained, the world can never make it wrong.?
Changes during training can change how a system performs.?
Adding new cards always removes the old answer.?
AI systems may need fixing more often than ordinary software.?
WHY THIS EXERCISEKnowing that training data ages helps a reviewer ask how a system is kept up to date.
FIX TINY TEXT THE CAREFUL WAY
  • ?Replace the stale cards with new cards.
  • ?Check that the model now gives the new hours.
  • ?Notice that the world changed: the new sign says nine.
  • ?Recount the tallies.
  • ?Find the training cards that are now out of date.
WHY THIS EXERCISERetraining is a careful cycle: notice, find, replace, recount and check.

Careful fixing, reviewer. Tomorrow is Impact Friday: what can we know about SH-1's own training data?

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