(A-1)

if there are m ways to make the first selection and n ways to make the second selectio, then there are m · n ways to makethe two selections.

an arrangement of some or all of a set of objects in a specific order. 

you can use the notation _np_r  to express the number of permutaions, when n equals the number of objects available and r equals the number of selections to make.

_np_{r =}     n!    

      (n - r)!

the product of the intergers from n down to 1 for any positive integer n.

n factorial is written as n! the value is 0! is defined to be 1.

4! = 4 x 3 x 2 x 1 = 24

any unordered selection of r objects from a set of n objects is a combination.

the number of combinations of n objects taken r at a time is _nC_r  =      n!        for 0 < r < n.

                    r!(n - r)!

the result of a single trial in a probability experiment.

all possible outcomes in a situation involving probability.

any group of outcomes in a situation involving probability.

how likely it is that an event will occur

P (event)

the ratio of the number of favorable outcomes to the number of possible outcomes if all outcomes have the same chance of happening.

P(event)= number of favorable outcomes

              number of possible outcomes

all possible outcomes that are not in the event.

P(complement of and event) = 1 - P(event)

a ratio that compares the number of favorable and unfavorable outcomes

Odds in favor =number of favorable outcomes 

                      number of unfavorable outcomes

Odds against=number of unfavorable outcomes

                       number of favorable outcomes

the ratio of the number of times an event actually happens to the number of times the experiment is done.

   P(event)= the number of times an event happens

              the number of times the experiment is done

(C-13)

an event that consists of more than two events linked by the word and or the word or .

When two events cannot happen at the same time, the events are mutually exclusive. 

if (A) and (B) are mutually exclusive events,

then P(A or B) = P(A) + P(B).

(C-15)

Events that have at least one common outcome.

If A and B are overlapping events,

then P(A or B) =P(A) + P(B) - P(A and B)

(C-16)

when the outcome of one event does not affect the probability of a second event, the events are independent.

If A and B are independent events,

then P(A and B) = P(A) • P(B)

(C-17)

when the outcome of one event affects the probability of a second event, the events are dependent events.

If A and B are dependent events,

then P(A then B) = P(A) • P(B after A)