# BIOL 2060 Lecture Notes - Continuous Or Discrete Variable, Mutual Exclusivity, Venn Diagram

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Probability

5.1 The probability of an event

Random trial: trial or process that has 2 or more possible outcomes whose

occurrences cannot be predicted.

Sample space: list of all possible outcomes of a random trial

Event: any potential subset of the sample space

Probability: proportion of all random trials in which the specified event occurs

when the same random process is repeated over and over again independently

and under the same conditions

Pr[A] =probability of event A

5.2 Venn diagrams

Venn diagram: area represents all possible outcomes of a random trial

5.3 mutually exclusive events

Mutually exclusive: both events cannot occur simultaneously

Pr[A and B]=0

5.4 Probability distribution

Probability distribution: list of the probabilities of all mutually exclusive outcomes

of a random trial

Discrete probability distribution: gives the probability of each possible value or

outcome of a discrete variable

Probability density: allows us to describe the probability of any range of values

(continuous probability distributions) , can find probability of a range by finding

the area under the curve

5.5 either this or that: adding probabilities

If events we are trying to combine are mutually exclusive, we can add

probabilities (either of the 2) OR statements

Probabilities of all mutually exclusive events add to one

Pr[not A]=1-Pr[A]

Pr[A or B]=Pr[A]+Pr[B]-Pr[A and B] .........not mutually exclusive