A mattress company has two stores, one in City X and the other in City Z. The company has advertised...
GMAT Two Part Analysis : (TPA) Questions
A mattress company has two stores, one in City X and the other in City Z. The company has advertised equally in newspapers in both cities, but has advertised twice as much on the radio in City Z as in City X. The two cities have similar populations and economies and the sales at each store have been roughly equal. A consultant claims this shows that the radio advertising has not improved mattress sales.
In the table below, select changes that the company could make in City X and City Z, respectively, that together would probably be most helpful in testing the consultant's claim. Make only two selections, one in each column.
Phase 1: Owning the Dataset
Argument Analysis Table
| Text from Passage | Analysis |
| "A mattress company has two stores, one in City X and the other in City Z" |
|
| "The company has advertised equally in newspapers in both cities" |
|
| "but has advertised twice as much on the radio in City Z as in City X" |
|
| "The two cities have similar populations and economies" |
|
| "and the sales at each store have been roughly equal" |
|
| "A consultant claims this shows that the radio advertising has not improved mattress sales" |
|
Argument Structure
- Main conclusion: Radio advertising has not improved mattress sales
- Supporting evidence: City Z has twice as much radio advertising but equal sales
- Key assumption: The current advertising mix allows us to isolate radio's effect
- Logical flow: Different radio advertising → Same sales → Radio doesn't work
Phase 2: Question Analysis & Prethinking
Understanding What Each Part Asks
We need to select changes for:
- Part 1 (City X): A change that helps test the consultant's claim
- Part 2 (City Z): A change that helps test the consultant's claim
- Key insight: The two changes must work together to create a valid test
Question Type and Prethinking
This is asking for changes that would test a claim. To test whether radio advertising works, we need to:
- Isolate the effect of radio advertising
- Remove confounding variables
- Create a cleaner comparison between the cities
Specific Prethinking for Each Part
For both cities: The best test would be to eliminate the newspaper advertising (which is currently equal) to see if the difference in radio advertising alone creates a difference in sales. This would:
- Remove the confounding variable (newspapers)
- Leave only radio advertising as the marketing difference
- Allow us to see if City Z's doubled radio advertising actually drives more sales
Phase 3: Answer Choice Evaluation
Evaluating Each Choice
"Double newspaper advertising"
- What it says: Increase newspaper ads to twice the current level
- For testing the claim: This adds more confounding variables rather than isolating radio's effect
- Not optimal for either city
"Eliminate newspaper advertising"
- What it says: Stop all newspaper advertising
- For testing the claim: This removes the equal variable, leaving only radio advertising differences
- Strong candidate for both cities - creates the cleanest test
"Eliminate radio advertising"
- What it says: Stop all radio advertising
- For testing the claim: This would test if radio has any effect, but doesn't test the consultant's specific claim about the current situation
- Could work but less direct than eliminating newspapers
"Change the content of radio advertising"
- What it says: Keep radio advertising but modify the message
- For testing the claim: Introduces a new variable (content quality) that complicates the test
- Not optimal for testing the original claim
"Add television advertising"
- What it says: Begin TV advertising
- For testing the claim: Adds another confounding variable
- Makes the test less clear, not more clear
The Correct Answers
- For Part 1 (City X): Eliminate newspaper advertising
- For Part 2 (City Z): Eliminate newspaper advertising
By eliminating newspaper advertising in both cities, we create a situation where:
- City X has only its baseline radio advertising
- City Z has only its doubled radio advertising
- If sales remain equal → consultant is correct (radio doesn't work)
- If City Z sales increase → consultant is wrong (radio does work)
Common Traps to Highlight
Why not eliminate radio advertising?
- This seems logical but actually tests a different question (whether current radio advertising has any effect at all)
- We want to test the consultant's specific claim about the current radio advertising levels
Why not change strategies differently in each city?
- Making different changes in each city introduces new variables
- We want both cities to make the same change to maintain a controlled comparison
Why not add more advertising?
- Adding advertising (newspaper, TV) creates more confounding variables
- We need to simplify, not complicate, to isolate radio's effect