Likelihood of Events Basic

Probability -  by Ray Nanji 

Probability is a chance of an event occuring

Definition 

• the extent to which an event is likely to occur, measured by the ratio of the favourable cases to the whole number of cases possible

• the extent to which something is likely to happen or be the case

Keywords in Probability

• CHANCE - a possibility of something happening.

• Event - a thing that happens or takes place, especially one of importance.

• RANDOM - made, done, or happening without method or conscious decision.

• PREDICTABLE - An expected result

• Sample Space  - he sample space of an experiment or random trial is the set of all possible outcomes or results of that experiment.

• Bias -  Bias, prejudice mean a strong inclination of the mind or a preconceived opinion about something or someone. A bias may be favorable or unfavorable: bias in favor of or against an idea.

• Outcome - an outcome is a possible result of an experiment or trial. Each possible outcome of a particular experiment is unique, and different outcomes are mutually exclusive. All of the possible outcomes of an experiment form the elements of a sample space

The probability vocabulary and scale

• Probabilities go from 0 to 1 as decimals and fractions or from  0% to 100%

• A probability of 1 or 100 % is described as CERTAIN

• A probability of 0 is said to be IMPOSSIBLE 

• A probability of 50 % or 1/2 or 0.5 is described as being EVEN

•  A probability of between 0 and 0.5 or 0 and 1/2 or 0 % and 50 % is described as being UNLIKELY 

• A probability between 0.5 and 1or 1/2 and 1 or 50 % and 100 % is described as being LIKELY 

Types of Probabilities

• Experimental Probability or relative frequency - Experimental probability is probability that is determined on the basis of the results of an experiment repeated many times

• Theoretical Proability - Theoretical probability is probability that is determined on the basis of reasoning.

The Probability Scale 

The Probability formula

Multiple Choice

A die is rolled once. What is the probability of rolling a 5? Your answer should be a fraction in simplest form.

• 1/6

• 1/3

• 2/5

• 5/6

Multiple Choice

Probability can be written as ...

• fraction

• decimal

• percentage

• all the above

Multiple Choice

A likely chance event is closer to what number?

• 0

• 0.5

• 1

• 100

Multiple Choice

A bag contains 5 quarters, 2 dimes, and 4 pennies. What is the probability of picking a quarter?

• 6

• 5/6

• 1/3

• 5/11