Unit III Flashcards
What is probability used to determine?
The chance of an occurrence of an event; it is the mathematical measure of the likelihood of an event occurring.
Formula for probability?
Of favorable options divided by # of total possible options.
What are the 3 ways probability can be expressed as?
- Fraction
- Proportion
- Percentage
What is an outcome?
A particular result of any random process.
What is a sample space ?
The set of all possible outcomes; denoted by capital s
What is an event?
A list of all the favorable outcomes; denoted by any capital letter.
What are axioms of probability?
The basic laws on which probability and the discipline of probability have been built.
Axiom #1?
If A is an event, then the probability of A must be greater than or equal to 0 OR less than or equal to 1.
Axiom # 2?
The probabilities of all outcomes must sum to 1.
Axiom #3?
The probability of an event is the sum of all the probabilities for all the individual outcomes.
Axiom #4?
If the probability of an event is zero, then the event is considered impossible; if the probability of an event is 1 then it is certain to occur.
What is a complement?
All elements/everything not in the event of interest.
What is an intersection?
This represents all the elements in both events of interest.
What does the law of total probability state?
If you are interested in event A, then you can take the intersection and everything in A, but not in B.
What is union?
This is all the elements in all the events of interest.
What ate mutually exclusive events?
Two events that cannot occur together; for ie. You cannot be dead and alive at the same time.
What are independent events?
Events where the occurrence of one does not affect the occurrence of another event.
What is another term for contingency table?
Cross table
What is a contingency table?
A table which shows the frequency for the intersection of two categorical values.
What question does marginal probability answer?
How many times does one variable occur?
What is the formula for marginal probabilities?
Outside total divided by grand total.
What question does a joint probability answer?
How often does a combination of two variables occur?
What is the formula for joint probability?
Inside count divided by the grand total.
What are conditional probabilities ?
Probabilities which assign a fixed value to ONE variable, and look at the proportions/ percentages of other variables under that condition.
What question do conditional probabilities answer?
What is the proportion/percentage of one variable, given the specific value of the other category?
What is the formula for conditional probability?
Inside count divided by outside total.
What is the second formula for finding conditional probabilities?
The probability of A given B equals the probability of A intersect B divided by the probability of B.
