Warning: foreach() argument must be of type array|object, bool given in /var/www/html/web/app/themes/studypress-core-theme/template-parts/header/mobile-offcanvas.php on line 20

Consider the conditions of Exercise 23 in Sec. 2.2 again. Assume that Pr(B)=0.4. LetAbe the event that exactly 8 out of 11 programs compiled. Compute the conditional probability ofBgivenA.

Short Answer

Expert verified

The conditional probability of Bgiven Ais 0.3874

Step by step solution

01

Given information

Referring to exercise 23,

The probability of the task being easy is 0.4, and Ais the event that exactly 8 out of 11 programs were compiled.

02

State the events

Referring to exercise 23,

The events are

A= Exactly 8 out of 11 programs complied

B=The programming task was easy

03

State the probabilities

The probability of the task is easy,\(\Pr \left( B \right) = 0.4\)

So, the probability of the task being hard is\(\Pr \left( {{B^c}} \right) = 0.6\)

Referring to the result of exercise 23, we get,

The probability of exactly 8 out of 11 programs will compile given B,\(\Pr \left( {A\left| B \right.} \right) = 0.02214\)

And the probability of exactly 8 out of 11 programs will compile given\({B^c}\),

\(\Pr \left( {A\left| {{B^c}} \right.} \right) = 0.02234\)

04

Calculate the conditional probability

We have to compute the conditional probability of Bgiven A.

So, by the Bay’s theorem, we get,

\(\begin{aligned}{}{\bf{Pr}}\left( {{\bf{B}}\left| {\bf{A}} \right.} \right){\bf{ = }}\frac{{{\bf{Pr}}\left( {\bf{B}} \right){\bf{Pr}}\left( {{\bf{A}}\left| {\bf{B}} \right.} \right)}}{{{\bf{Pr}}\left( {\bf{B}} \right){\bf{Pr}}\left( {{\bf{A}}\left| {\bf{B}} \right.} \right){\bf{ + Pr}}\left( {{{\bf{B}}^{\bf{c}}}} \right){\bf{Pr}}\left( {{\bf{A}}\left| {{{\bf{B}}^{\bf{c}}}} \right.} \right)}}\\ = \frac{{0.4 \times 0.02214}}{{\left( {0.4 \times 0.02214} \right) + \left( {0.6 \times 0.02334} \right)}}\\ = 0.3874\end{aligned}\)

Therefore, the conditional probability is 0.3874.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Suppose that three red balls and three white balls are thrown at random into three boxes and and that all throws are independent. What is the probability that each box contains one red ball and one white ball?

Suppose that there is a probability of\(\frac{1}{{50}}\)that you will win a certain game. If you play the game 50 times, independently, what is the probability that you will win at least once?

Three prisonersA,B, andCon death row know that exactly two of them are going to be executed, but they do not know which two. PrisonerAknows that the jailer will not tell him whether or not he is going to be executed. He, therefore, asks the jailer to tell him the name of one Prisoner other thanAhimself who will be executed. The jailer responds thatBwill be executed. Upon receiving this response, PrisonerAreasons as follows: Before he spoke to the jailer, the probability was \(\frac{2}{3}\) that he would be one of the two prisoners executed. After speaking to the jailer, he knows that either he or PrisonerCwill be the other one to be executed. Hence, the probability that he will be executed is now only \(\frac{1}{2}\). Thus, merely by asking the jailer his question, the Prisoner reduced the probability that he would be executed \(\frac{1}{2}\)because he could go through exactly this same reasoning regardless of which answer the jailer gave. Discuss what is wrong with prisonerA’s reasoning.

Suppose that a box contains five coins and that for each coin there is a different probability that a head will be obtained when the coin is tossed. Let \({{\bf{p}}_{\bf{i}}}\)denote the probability of a head when theith coin is tossed \({\bf{i = }}\left( {{\bf{1, \ldots ,5}}} \right)\) and suppose that \({{\bf{p}}_{\bf{1}}}{\bf{ = 0}}\),\({{\bf{p}}_{\bf{2}}}{\bf{ = }}\frac{{\bf{1}}}{{\bf{4}}}\) ,\({{\bf{p}}_{\bf{3}}}{\bf{ = }}\frac{{\bf{1}}}{{\bf{2}}}\) ,\({{\bf{p}}_{\bf{4}}}{\bf{ = }}\frac{{\bf{3}}}{{\bf{4}}}\) , and \({{\bf{p}}_{\bf{5}}}{\bf{ = 1}}\).

  1. Suppose that one coin is selected at random from the box and when it is tossed once, a head is obtained. What is the posterior probability that theith coin was selected \({\bf{i = }}\left( {{\bf{1, \ldots ,5}}} \right)\)?
  2. If the same coin were tossed again, what would be the probability of obtaining another head?
  3. If a tail had been obtained on the first toss of the selected coin and the same coin were tossed again, what would be the probability of obtaining a head on the second toss?

Use the prior probabilities in Example 2.3.8 for the events\({B_1},...,{{\bf{B}}_{11}}\). Let \({E_1}\)be the event that the first patient is a success. Compute the probability of \({E_1}\) and explain why it is so much less than the value computed in Example 2.3.7.

See all solutions

Recommended explanations on Math Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free