Reading 8: Probability Concepts-LOS g 习题精选 2011, following, between, border

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Session 2: Quantitative Methods: Basic Concepts
Reading 8: Probability Concepts

LOS g: Distinguish between dependent and independent events.

 

 

If X and Y are independent events, which of the following is most accurate?

A) P(X | Y) = P(X).

B) P(X or Y) = (P(X)) × (P(Y)).

C) P(X or Y) = P(X) + P(Y).

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Note that events being independent means that they have no influence on each other. It does not necessarily mean that they are mutually exclusive. Accordingly, P(X or Y) = P(X) + P(Y) ? P(X and Y). By the definition of independent events, P(X|Y) = P(X).

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A company says that whether it increases its dividends depends on whether its earnings increase. From this we know:

A) P(both dividend increase and earnings increase) = P(dividend increase).

B) P(earnings increase | dividend increase) is not equal to P(earnings increase).

C) P(dividend increase | earnings increase) is not equal to P(earnings increase).

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If two events A and B are dependent, then the conditional probabilities of P(A | B) and P(B | A) will not equal their respective unconditional probabilities (of P(A) and P(B), respectively). Both remaining choices may or may not occur, e.g., P(A | B) = P(B) is possible but not necessary.

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If the outcome of event A is not affected by event B, then events A and B are said to be:

A) conditionally dependent.

B) statistically independent.

C) mutually exclusive.

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If the outcome of one event does not influence the outcome of another, then the events are independent.