5.1 Basics of Probability

Question 1

Probability Experiment

Answer 1

Once in which we do not know what any individual outcome will be, but we do know how a long series of repetitions will come out.

Question 2

Probability

Answer 2

The proportion of times that the event occurs in the long run, as a probability experiment is repeated over and over again.

Question 3

Law of Large Numbers

Answer 3

Says that as a probability experiment is repeated again and again, the proportion of times that a given event occurs will approach its probability.

Question 4

Sample Space

Answer 4

Contains all the possible outcomes of a probability experiment.

Question 5

Statistical Event

Answer 5

An outcome or a collection of outcomes from a sample space.

Question 6

Probability Model

Answer 6

Used in a probability experiment. Consists of a sample space, along with a probability for each event.

Notation: If A denotes an event, the probability of the event A is denoted P(A).

Question 7

Computing Probabilities with Equally Likely Outcomes

Answer 7

If a sample space has n equally likely outcomes, and an event A has k outcomes, then

P(A) = (Number of outcomes in A) / (Number of outcomes in the sample space) = k / n

Question 8

Event Probability

Answer 8

The probability of an event is always between 0 and 1. In other words, for any event A, 0 <= P(A) <= 1.

If A cannot occur, then P(A) = 0.
If A is certain to occur, then P(A) = 1

Question 9

Unusual Event

Answer 9

One whose probability is small.

Sometimes people use the cutoff 0.05; that is, they consider any event whose probability is less than 0.05 to be unusual. But there are not hard and fast rules about this.

Question 10

Empirical Method

Answer 10

Consists of repeating an experiment a large number of times, and using the proportion of times an outcome occurs to approximate the probability of the outcome.

Question 11

Simulation

Answer 11

A virtual experiment.