Probability Flashcards
1
Q
random trial
A
- process or experiment that has 2+ possible outcomes whose occurrence cannot be predicted with certainty
2
Q
event (of interest)
A
- any potential subset/options from all the potential outcomes
3
Q
probability
A
- proportion of times the event would occur if we repeated a random trial over and over again under the same conditions, the true relative frequency
- ranges from 0 - 1
4
Q
proportion
A
- fraction of individuals having a particular attribute
- (number with attribute)/n
5
Q
mutually exclusive
A
- 2 events are mutually exclusive if they cannot both be true
- P[A and B] = 0
6
Q
probability distribution (2)
A
- describes the true relative frequency of all possible values of a random frequency
- list of the probabilities of all mutually exclusive outcomes of a random trial
7
Q
the addition principle
A
- it two events A and B are mutually exclusive then : P[A OR B] = Pr[A] + Pr[B]
8
Q
what is the probability of an event not occurring?
A
- Pr[not A] = 1 - Pr[A]
9
Q
general addition rule
A
- Pr[A or B] = Pr[A] + Pr[B] - Pr[A and B]
10
Q
independence
A
- two events are independent if the occurrence of one gives no info about whether the second will occur
11
Q
multiplication rule
A
- if two events A and B are independent, then: Pr[A AND B] = Pr[A] x Pr[B]
12
Q
when probability statements use “OR”
A
- involves addition: Pr[A or B] = Pr[A] + Pr[B], of the 2 events are mutually exclusive
13
Q
when probability statements use “AND”
A
- involves multiplication: Pr[A and B] = Pr[A] x Pr[B] when A and B are independent
14
Q
what is the general formulae for “at least one” out of n independent trials
A
Pr[at least one A] = 1 - (1 - Pr[A])^n
15
Q
dependent events
A
- probability of one event depends on the outcome of another event
16
Q
conditional probability
A
- probability of event occurring given that a condition is met
- Pr[X|Y] = probability of X “given” Y
17
Q
general multiplication rule
A
Pr[A AND B] = Pr[A] * Pr[B|A]
18
Q
law of total probability
A
the probability of an event, A, is:
Pr[A] = All values of Pr[B] * Pr[A|B]
where B represents all possible mutually exclusive values of the conditions
