IXL - Write a discrete probability distribution (Algebra 2 practice)

Andrew counted the number of problems on each of his tests.

Number of problems	Number of tests
10	2
43	2
63	1
75	2
88	3

is the number of problems that a randomly chosen test had. Write the probability distribution of

in the table below.

Write each probability as a decimal.

X	P ( X )
10	0.2
43
63	0.1
75	0.2
88	0.3

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Learn with an example

question

For a social studies project, Sharon counted the number of classrooms in each school in the city.

Number of classrooms	Number of schools
18	4
75	5
84	1

is the number of classrooms that a randomly chosen school has. Write the probability distribution of

in the table below.

Write each probability as a decimal.

X	P ( X )
18	0.4
75	0.5
84

key idea

A random variable is a function that assigns a numerical value to each outcome in a sample space. Note that though random variables are functions, they are usually denoted by letters like

is a random variable,

(

)

(

)

is the probability that

takes the value

The function that maps

(

)

is the probability distribution of

A probability distribution is frequently represented as an equation, table, or graph.

A uniform probability model is a sample space in which all outcomes are equally likely.

In a uniform probability model, the probability of an event

is the number of outcomes in that event divided by the total number of outcomes in the sample space:

(

)

# of outcomes in

total # of outcomes

solution

Each school is equally likely to be chosen. So, to find the probability that a school that has a particular number of classrooms is chosen, divide the frequency of that number of classrooms by the total number of schools.

Count the total number of schools.

Add the frequencies of each number of classrooms to find the total number of schools:

Write the probability distribution of

Divide each frequency by 10 to find the probability that a school chosen at random has a particular number of classrooms.

X	P ( X )
18	0.4
75	0.5
84	0.1

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