Study Guide and Intervention (continued) - MathnMind
Study Guide and Intervention (continued) - MathnMind
Study Guide and Intervention (continued) - MathnMind
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14-4<br />
NAME ______________________________________________ DATE______________ PERIOD _____<br />
<strong>Study</strong> <strong>Guide</strong> <strong>and</strong> <strong>Intervention</strong><br />
Probability Distributions<br />
R<strong>and</strong>om Variables <strong>and</strong> Probability Distributions A r<strong>and</strong>om variable X is a<br />
variable whose value is the numerical outcome of a r<strong>and</strong>om event.<br />
Example<br />
A teacher asked her students how many<br />
siblings they have. The results are shown in the table at<br />
the right.<br />
a. Find the probability that a r<strong>and</strong>omly selected student<br />
has 2 siblings.<br />
The r<strong>and</strong>om variable X can equal 0, 1, 2, 3, or 4. In the table,<br />
the value X 2 is paired with 8 outcomes, <strong>and</strong> there are<br />
27 students surveyed.<br />
2 siblings<br />
P(X 2) <br />
27 students surveyed<br />
<br />
8<br />
The probability that a r<strong>and</strong>omly selected student has 2 siblings is , or 29.6%.<br />
27<br />
b. Find the probability that a r<strong>and</strong>omly selected student has at least three siblings.<br />
P(X 3) <br />
1<br />
The probability that a r<strong>and</strong>omly selected student has at least 3 siblings is , or 11.1%.<br />
9<br />
Exercises<br />
8<br />
27<br />
2 1<br />
27<br />
For Exercises 1–3, use the grade distribution<br />
shown at the right. A grade of A 5, B 4,<br />
C 3, D 2, F 1.<br />
1. Find the probability that a r<strong>and</strong>omly selected<br />
student in this class received a grade of C.<br />
2. Find the probability that a r<strong>and</strong>omly selected student in this class received a grade<br />
lower than a C.<br />
3. What is the probability that a r<strong>and</strong>omly selected student in this class passes the course,<br />
that is, gets at least a D?<br />
4. The table shows the results of tossing 3 coins<br />
50 times. What is the probability of getting<br />
2 or 3 heads?<br />
X Grade 5 4 3 2 1<br />
Number of<br />
Students<br />
Number of Number of<br />
Siblings Students<br />
0 1<br />
1 15<br />
2 8<br />
3 2<br />
4 1<br />
6 9 5 4 1<br />
X Number of Heads 0 1 2 3<br />
Number of Times 6 20 19 5<br />
© Glencoe/McGraw-Hill 849 Glencoe Algebra 1<br />
Lesson 14-4
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