The new gre pays more attention to the examination of basic ability in order to really improve the English level of candidates. Although the difficulty coefficient of the new gre math test has increased, the new gre math can't run out of the knowledge range of senior three at most. It should be reminded that difficulties do not pose a threat to us. As candidates, we should give full play to our own advantages and understand the new gre mathematical conditions and the test sites frequented by independent events. Here are the common conclusions of the new GRE mathematics: conditions and independent event probability.

3) Conditional probability: Considering the probability of event B when event A has already occurred.

Definition: Let A and B be two events, P (a) >; 0, indicating

P(B|A)=P(A*B)/P(A) .................... formula 3

Is the probability that event B will happen if event A has already happened.

Understanding: it is P (intersection of A and B) /P (set A)

Understand:? What is the probability that event B will happen when event A has already happened? Obviously, when saying this sentence, both A and B happened, and we require the ratio of A and B happening at the same time to A, that is, the probability ratio of A and B happening at the same time to A. ..

Total probability theorem

The occurrence of event A always occurs under some other conditions, such as B, C and D, which means that the probability of A is actually the sum of the probabilities of A under the conditions of B, C and D. A has conditional probability when B occurs, C occurs and D occurs. If b, c and d contain all the conditions of a, then, a?

P(A)=P(A|B)+P(A|C)+P(A|D)

4) Independent events and probabilities

The two events are independent, that is to say, whether A and B occur or not does not affect each other. A is a, b is b, expressed by the formula P(A|B)=P(A), then the probability of two things happening at the same time is:

P(A U B)=P(A)？ P(B) ................ formula 4

I hope that the above common conclusions about conditions and the probability of independent events will be helpful to everyone, and it is very useful to keep these knowledge in mind. I wish you all success in the GRE exam!