Probability
Vocabulary Foldable
Simple Event
FOLD
Sample Space
Fold
edges to
center
and label
outside
like this
Probability
Relative Frequency
Complement
Independent
Events
Compound Event
Addition Principle
FOLD
Sample Space Definition & Example
The list of all
possible
outcomes for an
activity.
Pairs of Socks in Drawer
2 black
3 white
1 pink
1 green
Activity –
picking 1
pair of
socks
Probability Definition & Example
The chance an event will happen.
P(black) = 2/7
Written as a number from 0 to 1.
P(white) = 3/7
Impossible event - probability 0
P(green) = 1/7
Certain event – probability 1
P(orange) = 0 – no orange socks
Probability of event Z; P(Z)
P(black, or white, or green, or pink)
=7/7 or 1 or 100%
number of ways an event can occur
number of possible outcomes
Can be written as a decimal, fraction or percent
Relative Frequency Definition &
Example
The number of
times an outcome
occurs divided by
the total number of
trials or times
attempted.
P(pink) = 1/7
Many trials –
relative frequency
= theoretical
probability
So… Relative
frequency = 2/2 or
100%
I pick from the box
2 times and get
pink both times.
Complement Definition & Example
The opposite of an
event happening
P(black) = 2/7
P(not black) or P(black’)
= 1-(2/7) or 5/7
Simple Event Definition & Example
An event with just
one outcome
possible at a time.
Represented by one
branch of a tree
diagram.
Drawing one sock from
the box. Only one
pair/color is possible.
Independent Events Definition &
Example
Events that have no
impact on how each
other turn out.
Drawing a pair of socks
from the drawer and
pulling out a pair of
earrings from a jewelry
box.
Compound Event Definition &
Example
An event made up Picking a black
of 2 or more
sock , replacing it,
simple events.
AND picking a
green sock.
2/7 * 1/7 = 2/49
MULTIPLY to get Probability of Compound Events
One Event AND Another Event - MULTIPLY
Addition Principle Definition &
Example
If outcomes of 2
simple events are
mutually exclusive
(none the same),
ADD their
probability to find
probability of both
happening.
Pick a pink sock OR
pick a white sock.
1/7 + 3/7 = 4/7
One Event OR Another Event - ADD