In a study conducted in Canada, servers in various restaurants wrote "Thank you" on randomly selected bills before presenting the...

GMAT Critical Reasoning : (CR) Questions

Source: Official Guide

Critical Reasoning

Assumption

MEDIUM

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Notes

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In a study conducted in Canada, servers in various restaurants wrote "Thank you" on randomly selected bills before presenting the bills to their customers. Tips on these bills were an average of three percentage points higher than tips on bills without the message. Therefore, if servers in Canada regularly wrote "Thank you" on restaurant their average income from tips would be significantly higher than it otherwise would have been.

Which of the following is an assumption on which the argument relies?

The "Thank you" messages would have the same impact on regular patrons of a restaurant as they would on occasional patrons of the same restaurant.

Regularly seeing "Thank you" written on their bills would not lead restaurant patrons to revert to their earlier tipping habits.

The written "Thank you" reminds restaurant patrons that tips constitute a significant part of the income of many food servers.

The rate at which people tip food servers in Canada does not vary with how expensive a restaurant is.

Virtually all patrons of the Canadian restaurants in the study who were given a bill with "Thank you" written on it left a larger tip than they otherwise would have.

Solution

Passage Analysis:

Text from Passage	Analysis
In a study conducted in Canada, servers in various restaurants wrote "Thank you" on randomly selected bills before presenting the bills to their customers.	What it says: A Canadian study had servers write "Thank you" on some bills but not others What it does: Sets up the basic experiment - creates controlled conditions for comparison What it is: Study design/methodology Visualization: Restaurant A: 100 bills → 50 get "Thank you", 50 don't
Tips on these bills were an average of three percentage points higher than tips on bills without the message.	What it says: Bills with "Thank you" got 3% higher tips than bills without it What it does: Provides the key finding that connects the written message to better tips What it is: Study results/evidence Visualization: Regular bill: 15% tip vs "Thank you" bill: 18% tip
Therefore, if servers in Canada regularly wrote "Thank you" on restaurant their average income from tips would be significantly higher than it otherwise would have been.	What it says: If servers always wrote "Thank you", they'd make much more tip money overall What it does: Makes a broad prediction based on the limited study results What it is: Author's conclusion Visualization: Server's monthly tips: $800 (no messages) vs $1,200 (with messages)

Argument Flow:

The argument moves from a specific study showing that "Thank you" messages increased tips by 3% to a general conclusion that regular use of such messages would significantly boost servers' overall tip income.

Main Conclusion:

If servers in Canada regularly wrote "Thank you" on bills, their average tip income would be significantly higher.

Logical Structure:

The argument uses one study's results as evidence to support a broader claim about what would happen if this practice became regular. The connection assumes that the 3% increase shown in the study would translate to significantly higher overall income if used consistently.

Prethinking:

Question type:

Assumption - We need to find what the argument must assume to be true for the conclusion to follow logically from the evidence

Precision of Claims

The argument makes specific claims about frequency (regularly writing messages), quantity (3 percentage point increase), and activity (writing thank you messages), moving from limited study results to broad predictions about income

Strategy

We'll identify ways the conclusion could fail even if the study facts remain true. The argument jumps from a limited study to claiming regular use would significantly increase income. We need to find what gaps the argument assumes away - like whether the effect would persist over time, whether other factors might interfere, or whether the effect size would remain the same

Answer Choices Explained

The "Thank you" messages would have the same impact on regular patrons of a restaurant as they would on occasional patrons of the same restaurant.

This focuses on the difference between regular vs. occasional patrons, but this isn't what the argument relies on. The study used randomly selected bills, which would have included both types of patrons already. The argument's leap is from occasional use to regular use of the messages, not about different types of customers. This isn't an assumption the argument requires.

Regularly seeing "Thank you" written on their bills would not lead restaurant patrons to revert to their earlier tipping habits.

This directly addresses the core gap in the argument. The study showed results when messages appeared on randomly selected bills (occasionally), but the conclusion claims regular use would significantly increase income. If customers got used to seeing the messages regularly and stopped responding with higher tips, the conclusion would fail even if the study results remain valid. The argument MUST assume this won't happen - making this the correct assumption.

The written "Thank you" reminds restaurant patrons that tips constitute a significant part of the income of many food servers.

This explains a possible mechanism for why the messages work, but the argument doesn't need to assume this specific reason. The messages could work for other psychological reasons (politeness, reciprocity, etc.) and the argument would still hold. Since the argument can succeed without this being true, it's not an assumption.

The rate at which people tip food servers in Canada does not vary with how expensive a restaurant is.

This addresses variation across different restaurant types, but the argument doesn't rely on this. The study included 'various restaurants' which likely had different price points, and the 3% increase was found across this range. The argument's conclusion about regular use doesn't depend on tip rates being uniform across restaurant types.

Virtually all patrons of the Canadian restaurants in the study who were given a bill with "Thank you" written on it left a larger tip than they otherwise would have.

This is too extreme - the argument only needs the average to be higher, not for virtually everyone to tip more. Some people might tip the same or even less, but as long as the overall average increases, the argument works. The argument doesn't assume this universal response.

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