Download Sec. 6-2 - AASDGonzalez

Chapter 6
Sec. 6-2
1. Random Variables:
Variables whose values are determined
by chance. (The variable itself
represents a concept and could have
several values)
X represents the number of A’s on a report
card.
X = 0, 1, 2, 3, 4, 5, 6, 7, or 8
a. Discrete Variables:
Variables whose values are “countable”
as whole numbers.
The number of A’s in a class. {0, 1, 2,…25}
The number of tires on a car. {0, 1, 2, 3, 4}
b. Continuous Variables:
Variables whose values are
“scientifically” measured. (Technically, the
values are irrational, but we make them
“discrete” by rounding.)
The speed of a car {55.12425 mph
Temperatures {45.123°
=
=
55mph}
45°}
The Biggest Loser’s weight {245.532lbs. = 246 lbs.}
2. Probability Distribution:
A table or chart used to represent the
probability for EACH value of a random
variable.
(Label the horizontal & vertical axes.)
– The sum of the p(x)’s of the sample
space must equal 1. Σp(x) = 1
– Each event’s p(x) must be between
zero and one inclusive: 0 ≤ p(x) ≤ 1.
Construct a p(x) distribution for the number
of girls in a 3 child family.
Let x = number of girls . . . 0, 1, 2, or 3
To determine the p(x) of each event you
could use the sample space:
{GGG, GGB, GBG, BGG, GBB, BGB, BBG, BBB}
x
p(x)
0
1/8
1
3/8
2
3/8
3
1/8
Number of Girls in a 3 Child Family
p(x)
3/8
2/8
1/8
0
1
2
3
Number of Girls