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Q26E

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Discrete Mathematics and its Applications
Found in: Page 467
Discrete Mathematics and its Applications

Discrete Mathematics and its Applications

Book edition 7th
Author(s) Kenneth H. Rosen
Pages 808 pages
ISBN 9780073383095

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Short Answer

Question: Let E be the event that a randomly generated bit string of length three contains an odd number of 1s, and let F be the event that the string starts with 1. Are E and F Independent?

Answer

The two events E and F are Independent events as PEF=PE×PF .

See the step by step solution

Step by Step Solution

Step 1: Given Information

E is the event that a randomly generated bit string of length three contains an odd number of 1s, and F is the event that the string starts with 1

Step 2: Definition of Independent Events

Independent events are those events whose occurrence is not dependent on any other event.

Two events are Independent if the equation P(EF)=P(E)×P(F) holds true.

Step 1: Given Information

E is the event that a randomly generated bit string of length three contains an odd number of 1s, and F is the event that the string starts with 1.

Step 3: Calculating the Probability

We know that, E is the event that a randomly generated bit string of length three contains an odd number of 1s.

In general, a bit has a single binary value, either 0 or 1.

Here, totally four bit strings of length three that contains an odd of 1s; 100, 010, 001, 111.

So, the event E becomes,

E=100,010,001,111andE=4]

Consider F be the event that the string starts with ‘1’.

Here, totally four bit strings of length three that starts with 1; 100, 110, 101, 111.

So, the event F becomes,

F=100,110,101,111andF=4

Next we find EF as

EF=100,010,001,111100,110,101,111 =100,111and,EF=2

In general, the sample space S of an experiment is the set of all possible outcomes.

In this experiment the set of all possible outcomes are 8.

Hence, they are, 000,010,001,100,110,011,101,111

So, S=8

Step 4: Determining whether the events E and F are Independent or not

Now, we determine that the events E and F are Independent or not, from the definition of Probability.

Suppose that E is an event that is a subset of sample space S, then the probability of an event E is defined as,

PE=ES-------1 Where, E is the number of outcomes in E, S is the total number of outcomes.

Now, from the definition of Independent sets, Let E and F are two events, then the events E and F are Independent only and only if

PES=PE×PS------2

Using (1) we find PE and PF as,

PE=ES=48=12andPF=FS=48=12

Next we find

PEF=EFS=28=14

We can write this as,

PEF=14 =12×2 =12×12 =PE×PF

Hence, PEF=PE×PF .

Therefore, the two events E and F are Independent.

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