Download Activity #27

Math 103 - Cooley
Statistics for Teachers
OCC
Activity #27 – Random Variables
California State Content Standard - Statistics, Data Analysis, and Probability
N/A
Random Variable
A random variable is a quantitative variable whose value depends on chance.
Discrete Random Variable
A discrete random variable is a random variable whose possible values can be listed.
Probability Distribution
A listing of possible values and corresponding probabilities of a discrete random variable, or a formula for the
probabilities.
Sum of the Probabilities of a Discrete Random Variable
For any discrete random variable X, we have  P( X  x)  1
Interpretation of a Probability Distribution
In a large number of independent observations of a random variable X, the proportion of times each
possible event occurs will approximate the probability of X.
 Exercises:
1)
2)
Class Activity: The data will be collected by each member of the class. Each student will write on
the board, the total number of natural siblings they have. Let the random variable X represent the
number of siblings each student has. Draw a probability distribution for the random variable X.
a)
What are the possible values that the random variable X can possibly take on?
b)
What are the values that the random variable X has taken on?
c)
Find P( X  1) .
d)
Find P( X  2) .
e)
Find P( X  3) .
f)
Find P( X  2) .
Class Activity: The data will be collected by each member of the class. Each student will write on
the board, the total number of letters in their legal last name. Let the random variable X represent
the number of letters in each student’s last name. Draw a probability distribution for the random
variable X.
a)
What are the possible values that the random variable X can possibly take on?
b)
What are the values that the random variable X has taken on?
c)
Find P(4  X  6) .
d)
Find P(5  X  8) .