OEA Admission Exam flashcards

31 cards. Read the term and the definition here. The deck at the top of this page is optional.

Percent change formula

Percent change equals the difference between new and old values divided by the old value, multiplied by 100. Always divide by the original amount, not the new one.

Successive percentage changes

Two consecutive changes of a% and b% combine multiplicatively as (1 + a/100)(1 + b/100). A rise and equal fall therefore produce a net decrease, never zero.

Harmonic mean for average speed

For equal distances traveled at speeds x and y, average speed is 2xy/(x + y). Using the arithmetic mean overstates the result because more time is spent at the slower speed.

Combined work rate

If worker A needs a days and worker B needs b days, working together they finish in ab/(a + b) days. Rates add; times do not.

Weighted mean

The weighted mean multiplies each value by its weight, sums the products, and divides by the total weight. Averaging group means directly is valid only when group sizes match.

Median versus mean

The median is the middle value of ordered data and resists outliers. The mean uses every value and shifts sharply when extreme observations are present.

Rule of 70

Doubling time under steady percentage growth is approximately 70 divided by the annual growth rate in percent. A 5% rate implies roughly 14 years to double.

Main idea identification

The main idea is the central claim the entire passage supports. A choice that is accurate but covers only one paragraph is a detail, not the main idea.

Necessary inference test

A valid inference must be true whenever the passage is true. If the text permits the stated fact but does not require it, the inference is invalid.

Out of scope answer

An answer choice is out of scope when it introduces a comparison, cause, or time frame the passage never addresses, even if the claim is plausible in general.

EXCEPT question strategy

In EXCEPT or NOT questions, four choices are supported by the passage and one is not. Eliminate the supported options and select the remaining unsupported statement.

Author tone qualifiers

Words such as arguably, largely, and in most cases signal a qualified or moderate stance. Answer choices claiming certainty or hostility must match such hedging.

Para-jumble opening sentence

The first sentence of a rearranged paragraph usually contains no backward-referencing pronouns or connectors. Sentences beginning with this, these, or however rarely open the passage.

Vocabulary in context

To resolve a word's meaning, substitute each option into the original sentence and keep the one preserving the passage's logic. Dictionary priority order is irrelevant here.

Contrapositive validity

From 'if P then Q' one may validly infer 'if not Q then not P'. The converse and the inverse are not logically equivalent to the original statement.

Only if condition

'P only if Q' translates to 'if P then Q', making Q a necessary condition for P. P is sufficient for Q but Q does not guarantee P.

Unless translation

'P unless Q' means 'if not Q then P'. The clause following unless states the exception that would prevent P from occurring.

Sufficient versus necessary

A sufficient condition guarantees the outcome; a necessary condition is required but may not guarantee it. Treating necessary as sufficient is a standard logical flaw.

Valid syllogism forms

All A are B plus All B are C yields All A are C. Some A are B plus All B are C yields Some A are C. Other combinations require careful checking.

Seating arrangement method

Place the most constrained element first, then apply each rule as a constraint. Testing answer choices for rule violations is faster than building every full arrangement.

Correlation versus causation

Two variables moving together does not establish that one causes the other. Post hoc reasoning, which assumes sequence implies cause, is the most common version of this error.

Subject-verb agreement rule

The verb agrees with the head noun, ignoring intervening prepositional phrases. With neither/nor, the verb matches the subject nearer to it.

Dangling modifier

An introductory participial phrase must describe the subject of the main clause. Otherwise the phrase attaches to the wrong noun and the sentence becomes illogical.

Semicolon versus colon

A semicolon joins two independent clauses. A colon must follow a complete clause and introduces an explanation, list, or elaboration.

Parallel structure requirement

Items in a series and elements joined by and, or, or but must share grammatical form. Mixing infinitives, gerunds, and nouns breaks parallelism.

Affect versus effect

Affect is normally a verb meaning to influence. Effect is normally a noun meaning result, though effect can be a verb meaning to bring about.

Comma splice

Joining two independent clauses with only a comma is an error. Repair it with a period, a semicolon, or a coordinating conjunction.

Order of operations

Evaluate parentheses first, then exponents, then multiplication and division left to right, then addition and subtraction left to right. This sequence is standard in arithmetic.

Pigeonhole principle

Placing n items into k containers guarantees some container holds at least the ceiling of n divided by k items. Useful for proving existence without construction.

Permutations versus combinations

Permutations count ordered arrangements using n!/(n−r)!. Combinations count unordered selections using n!/(r!(n−r)!). Order matters only in the former.

Probability of at least one

The probability that an event occurs at least once equals one minus the probability it never occurs. This avoids summing overlapping cases directly.