Unit III

Question 1

What is probability used to determine?

Answer 1

The chance of an occurrence of an event; it is the mathematical measure of the likelihood of an event occurring.

Question 2

Formula for probability?

Answer 2

Of favorable options divided by # of total possible options.

Question 3

What are the 3 ways probability can be expressed as?

Answer 3

1. Fraction
2. Proportion
3. Percentage

Question 4

What is an outcome?

Answer 4

A particular result of any random process.

Question 5

What is a sample space ?

Answer 5

The set of all possible outcomes; denoted by capital s

Question 6

What is an event?

Answer 6

A list of all the favorable outcomes; denoted by any capital letter.

Question 7

What are axioms of probability?

Answer 7

The basic laws on which probability and the discipline of probability have been built.

Question 8

Axiom #1?

Answer 8

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.

Question 9

Axiom # 2?

Answer 9

The probabilities of all outcomes must sum to 1.

Question 10

Axiom #3?

Answer 10

The probability of an event is the sum of all the probabilities for all the individual outcomes.

Question 11

Axiom #4?

Answer 11

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.

Question 12

What is a complement?

Answer 12

All elements/everything not in the event of interest.

Question 13

What is an intersection?

Answer 13

This represents all the elements in both events of interest.

Question 14

What does the law of total probability state?

Answer 14

If you are interested in event A, then you can take the intersection and everything in A, but not in B.

Question 15

What is union?

Answer 15

This is all the elements in all the events of interest.

Question 16

What ate mutually exclusive events?

Answer 16

Two events that cannot occur together; for ie. You cannot be dead and alive at the same time.

Question 17

What are independent events?

Answer 17

Events where the occurrence of one does not affect the occurrence of another event.

Question 18

What is another term for contingency table?

Answer 18

Cross table

Question 19

What is a contingency table?

Answer 19

A table which shows the frequency for the intersection of two categorical values.

Question 20

What question does marginal probability answer?

Answer 20

How many times does one variable occur?

Question 21

What is the formula for marginal probabilities?

Answer 21

Outside total divided by grand total.

Question 22

What question does a joint probability answer?

Answer 22

How often does a combination of two variables occur?

Question 23

What is the formula for joint probability?

Answer 23

Inside count divided by the grand total.

Question 24

What are conditional probabilities ?

Answer 24

Probabilities which assign a fixed value to ONE variable, and look at the proportions/ percentages of other variables under that condition.

Question 25

What question do conditional probabilities answer?

Answer 25

What is the proportion/percentage of one variable, given the specific value of the other category?

Question 26

What is the formula for conditional probability?

Answer 26

Inside count divided by outside total.

Question 27

What is the second formula for finding conditional probabilities?

Answer 27

The probability of A given B equals the probability of A intersect B divided by the probability of B.