Show that one outcome of a double shift is genuinely indeterminate
Three steps, the way the exam actually works: work through the lab, write down your own measurements, then answer a 6-point free response. What you recorded goes to the grader with your writing, so a conclusion that does not follow from your own numbers will cost you the point — exactly as it would with a real reader.
Predict before you look
- A rightward shift of demand alone raises both price and quantity. What does a rightward shift of supply alone do to each?
- If two effects push a variable in opposite directions, what extra information would you need to say which way it ends up moving?
Nothing to submit here — these are to think through, so the prediction below is an informed one rather than a guess.
Commit to an answer now. It is not graded and being wrong costs nothing — the point is to have something specific to reconcile against once you have the data.
Answer every prediction to unlock the lab. A sentence is enough.
Run the investigation
Predictions first
The procedure and the simulation unlock once you have committed above. Observing before predicting is how a wrong intuition survives a lab intact.
Record what you measured
These are your numbers, not ours. The grader sees them, so your conclusions have to follow from what you actually recorded.
| Equilibrium price at reset | |
|---|---|
| Equilibrium quantity at reset | |
| Price after demand right only | |
| Quantity after demand right only | |
| Price after supply right only | |
| Quantity after supply right only | |
| Price after demand right AND supply right | |
| Quantity after demand right AND supply right | |
| Price after demand right AND supply left | |
| Quantity after demand right AND supply left |
Answer the free response
This exercise tests the claim that when both curves shift, exactly one of price and quantity is indeterminate. (a) Using your two single-shift trials, state the direction each shift alone moved price and quantity. (b) In your both-right trial, one variable changed and the other did not. Identify which, and explain why your two single-shift trials predict exactly that result. (c) Repeat the reasoning for your demand-right-with-supply-left trial: identify which variable was unchanged and explain why. (d) Your unchanged variable came out exactly unchanged rather than merely ambiguous. Explain what feature of this particular simulation produced that, and describe a specific change to your procedure that would make the same variable move in a definite direction.
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