Masterclass: SC – Comparison Errors • GMATCourse.mba

Core Philosophy: Apples Must Match Apples

Comparison questions test whether the items being compared are grammatically and logically parallel. Every comparison must compare like to like — a noun to a noun, a verb phrase to a verb phrase, and an idea to the same type of idea. The GMAT exploits our tendency to read quickly and miss when a comparison illogically contrasts two different categories of thing.

Comparison errors come in two forms: structural (grammatical mismatch) and logical (semantic mismatch). Both are equally important on the GMAT.

Core Insight: After words like "than," "like," "unlike," "as...as," and "compared to," always ask: what is being compared to what? Both sides must be the same category of thing.

Comparison Anatomy

Dissecting a Comparison

Faulty Comparison

"The profits of Company A are higher than Company B."

Comparing profits (noun phrase) to Company B (an entity). Wrong category.

↓ Fix

Correct Comparison

"The profits of Company A are higher than those of Company B."

"Those of" acts as a pronoun replacing "the profits of" — now profits are compared to profits.

Comparison Fix Strategy

Identify the comparison trigger word

"than," "as...as," "like," "unlike," "compared to," "more/less than," "similar to" — these signal a comparison is happening.

Label each side of the comparison

What is on the left of "than"? What is on the right? Write them out explicitly.

Check logical and grammatical parallelism

Both sides must be the same type of thing (noun, noun phrase, verb phrase, clause) AND the same semantic category (people vs. people, costs vs. costs).

Use "that of" / "those of" / "the same" for noun corrections

These pronoun replacements let you compare like-to-like: "the cost of X is higher than that of Y" (not "than Y").

Worked Examples

Example 1 — "Than" with a Noun

✗ The CEO's salary is higher than the senior directors.

✓ The CEO's salary is higher than that of the senior directors.

Salary vs. directors (wrong). "That of" makes it salary vs. salary.

Example 2 — "Like" vs. "As"

✗ Like the research showed, the drug was effective.

✓ As the research showed, the drug was effective.

"Like" compares nouns; "as" introduces clauses. "The research showed" is a clause → use "as."

Example 3 — "Unlike" Comparison

✗ Unlike most companies, the product line has remained consistent.

✓ Unlike those of most companies, the product line has remained consistent.

"Unlike" must compare the same category. Comparing "companies" to "product line" is illogical.

10 Comparison Traps

1. "Than" with entity instead of attribute

Comparing "salary" to "the directors" instead of "salary" to "the salary of the directors."

2. "Like" used for clauses

"Like" must compare nouns; "as" compares clauses. "Like the report found" is wrong.

3. Ambiguous "that" reference

"That" must clearly refer back to the noun being compared — avoid ambiguous pronoun references.

4. Singular/plural mismatch in "that of" / "those of"

"That of" for singular nouns; "those of" for plural nouns.

5. False equivalence via context

Structurally parallel comparisons that are logically nonsensical.

6. Incomplete comparison

"X is better" — better than what? GMAT requires explicit comparators.

7. "As much as" vs. "as many as"

"As much as" for uncountable quantities; "as many as" for countable. A common GMAT trap.

8. "More than" vs. "greater than"

"More than" for quantities; "greater than" for measurements and values. Context-specific.

9. Nested comparison confusion

A sentence with multiple comparisons — confirm that each compares the same type.

10. Double comparison

"More better," "most highest" — never combine "more/most" with a comparative/superlative adjective.

Comparison Structures Reference

Structure	Correct Use	Common Error
X is higher than Y	Both sides are parallel nouns or clauses	One side is an attribute; other is an entity
like X, Y...	X and Y are both nouns of the same type	"Like" before a clause
as X does	Clause comparison using "as"	Using "like" before a verb clause
that of / those of	Substitute for noun phrase to maintain parallelism	Omitting "that of" leaving illogical comparison
as much as / as many as	Uncountable / countable distinction	Using "as much as" for countable nouns

10 GMAT-Style Practice Questions

Select your answer, then reveal the step-by-step explanation. Each question reflects real GMAT difficulty and format.

Question 1 of 10 GMAT Verbal

The annual expenditure on research by the pharmaceutical company is significantly greater than ____. Which option correctly completes the comparison?

Correct Answer: (B)

(B) is correct. We're comparing "annual expenditure on research by the pharmaceutical company" (a singular noun phrase) to the annual expenditure of the technology startup. "That of the technology startup" uses "that" as a singular pronoun substitute for "the annual expenditure." (A) compares expenditure to a company — wrong category. (C) "those of" is plural — wrong for singular "expenditure." (D) "the technology startup's" is grammatically awkward and ambiguous. (E) "what the technology startup" is incomplete and awkward.

Question 2 of 10 GMAT Verbal

Unlike ________, the new CEO's management style emphasizes employee autonomy and flat organizational structures. Which option creates a grammatically and logically correct comparison?

Correct Answer: (C)

(C) is correct. "Unlike" must introduce something comparable to "the new CEO's management style." (C) gives "the management style of most traditional executives" — management style vs. management style. (A) compares executives to management style — illogical. (B) "that of" is singular and refers back to a noun — but "that" would create an ambiguous reference here. (D) "those of" is plural — management style is singular. (E) "how" introduces a clause — "unlike" should introduce a noun.

Question 3 of 10 GMAT Verbal

The population density of Tokyo is considerably higher than ________. Which option correctly completes the comparison?

Correct Answer: (B)

(B) is correct. "Population density of Tokyo" (singular noun phrase) must be compared to "population density of New York City." "That of New York City" correctly substitutes for the full noun phrase. (A) compares population density to a city — wrong category. (C) "those" is plural — "density" is singular. (D) "New York City's population" is a different attribute (population, not population density). (E) introduces a clause — wrong structure after "than."

Question 4 of 10 GMAT Verbal

________ the traditional model, the new software framework allows developers to modify modules without recompiling the entire application. Which option correctly fills the blank?

Correct Answer: (C)

(C) is correct. The sentence describes a contrast between the new framework and the traditional model (the new framework allows something the traditional model presumably doesn't). "Unlike" signals this contrast correctly. (A) "Like" signals similarity — the sentence describes a difference. (B) "As with" could work for similarity. (D) "Similar as" is ungrammatical. (E) "As" introduces a clause — "the traditional model" is a noun phrase.

Question 5 of 10 GMAT Verbal

The average commute time for workers in metropolitan areas is nearly twice as long as ________. Which option correctly completes this sentence?

Correct Answer: (C)

(C) is correct. "The average commute time for workers in metropolitan areas" (singular) must be compared to the average commute time for workers in rural areas. "That of workers in rural areas" uses "that" as a singular substitute for the noun phrase. (A) compares commute time to rural areas — wrong category. (B) compares commute time to workers — still wrong category. (D) "those of" is plural — "average commute time" is singular. (E) "rural area workers do" creates a clause but the main sentence uses a noun comparison.

Question 6 of 10 GMAT Verbal

Researchers found that brain activity in patients with the disorder was more similar to ________ than to healthy adults without the disorder. Which option correctly completes this sentence?

Correct Answer: (B)

(B) is correct. "Brain activity in patients" (singular noun phrase) must be compared to brain activity in children. "That of children under twelve" correctly substitutes the singular noun. (A) compares brain activity to children — wrong category. (C) "those of" is plural. (D) "what children...show" is a clause and creates a structural mismatch. (E) "children's brains" changes the noun being compared.

Question 7 of 10 GMAT Verbal

The operating costs of the new facility are expected to be lower than ________ at the time of its initial construction. Which option correctly completes the comparison?

Correct Answer: (B)

(B) is correct. "Operating costs" is plural → "those of the original facility" uses the correct plural pronoun to substitute for the noun phrase. (A) compares costs to a facility — wrong category. (C) "that of" is singular — "costs" is plural. (D) "the original facility's costs" is acceptable but slightly awkward compared to the cleaner (B). (E) "operating the original facility" changes the meaning.

Question 8 of 10 GMAT Verbal

________ many of its predecessors, the new model features a modular design that allows individual components to be replaced without discarding the entire unit. Which option is correct?

Correct Answer: (B)

(B) is correct. The sentence describes a feature that distinguishes the new model from predecessors — the modular design is a contrast, not a similarity. "Unlike many of its predecessors" correctly signals this contrast. (A) "Like" signals similarity. (C) "As" would introduce a clause — "many of its predecessors" is a noun. (D) "Similar to how" is wordy and introduces a clause. (E) "Contrary with" is ungrammatical — should be "contrary to."

Question 9 of 10 GMAT Verbal

The company's market share in emerging markets is growing at twice the rate ________ in developed markets. Which option correctly completes the sentence?

Correct Answer: (E)

(E) is correct. "Twice the rate...as that in developed markets" — "that" substitutes for "the rate" in developed markets. Both sides compare rates. (A) "than the growth" is redundant and the structure "twice as...than" is wrong. (B) "as in developed markets" is elliptical but acceptable in some contexts — however, "as that in developed markets" is more precise on GMAT. (C) "of growth" doesn't complete the comparison structure. (D) "as it is growing" introduces a clause where a noun comparison is needed.

Question 10 of 10 GMAT Verbal

Scientists have discovered that the immune response to this new vaccine is nearly as strong as ________. Which option correctly completes the comparison?

Correct Answer: (B)

(B) is correct. "The immune response to the new vaccine" (singular) must be compared to the immune response produced by the original treatment. "That produced by the original treatment" uses "that" as a singular substitute. (A) compares immune response to individuals — wrong category. (C) "those" is plural — "immune response" is singular. (D) creates a clause with "what" — creates a structural mismatch. (E) "the original treatment produced" is a clause fragment that doesn't work cleanly.

Key Takeaways

1. Label both sides of every comparison

Left of "than/as/like" and right must be the same category of noun/phrase.

2. "That of" for singular, "those of" for plural

These substitutes maintain parallelism when comparing noun phrases.

"Like" for nouns, "as" for clauses

"Like John, Mary..." → noun. "As John does,..." → clause with verb.

4. "Unlike" must compare the same category

Both items after and before "unlike" must be the same type of thing.