/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 16 Driving tests in a certain city ... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

Driving tests in a certain city are relatively easy to pass the first time you take them. After going through training, the percentage of new drivers passing the test the first time is \(80 \% .\) If a driver fails the first test, there is chance of passing it on a second harder test, two weeks later. \(50 \%\) of the second-chance drivers pass the test. If the second test is unsuccessful, a third attempt, a week later, is given and \(30 \%\) of the participants pass it. Otherwise, the driver has to retrain and take the test after 1 year. a) Find the probability that a randomly chosen new driver will pass the test without having to wait one year. b) Find the probability that a randomly chosen new driver that passed the test did so on the second attempt.

Short Answer

Expert verified
a) 0.93; b) \(0.1075\).

Step by step solution

01

Define Probabilities for Each Attempt

Identify the probability of passing the driving test on each attempt. Let\( P_1 \) be the probability of passing on the first attempt, \( P_2 \) for the second attempt given the first was failed, and \( P_3 \) for the third attempt given the first two were failed:- \( P_1 = 0.80 \)- \( P_2 = 0.50 \)- \( P_3 = 0.30 \).
02

Calculate Probability of Passing by the Second Attempt

Calculate the probability of passing the test by the second attempt:the probability of failing the first test is \( 1 - P_1 = 0.20 \);the probability of passing on the second attempt given the first was failed is \( 0.20 \times P_2 = 0.20 \times 0.50 = 0.10 \).
03

Calculate Probability of Passing by the Third Attempt

Find the probability of passing by the third attempt:probability of failing the first two attempts is \( 0.20 \times (1 - P_2) = 0.20 \times 0.50 = 0.10 \);probability of passing on the third attempt given the first two attempts were failed is \( 0.10 \times P_3 = 0.10 \times 0.30 = 0.03 \).
04

Calculate Total Probability of Passing Without Retraining

Add together the probabilities for passing on the first, second, or third attempt:\[P = P_1 + (0.20 \times P_2) + (0.20 \times 0.50 \times P_3) = 0.80 + 0.10 + 0.03 = 0.93\].
05

Calculate Probability of Passing on the Second Attempt

The probability that a driver passes the test on the second attempt, given they did pass, is obtained by dividing the probability of passing on the second attempt by the total probability of passing within three tries:\[ P_{2\mid pass} = \frac{0.10}{0.93} \approx 0.1075 \].

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 91Ó°ÊÓ!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Conditional Probability
Conditional probability is a fundamental aspect of probability theory that tells us the likelihood of an event, given that another event has occurred. In our driving test problem, one of the interesting conditional probabilities is finding the chance of passing the test on the second attempt, given that the driver eventually passes without having to wait a year.

This involves a sequence of conditional events: first failing the initial test and then succeeding on the next try. Here, the probability of passing on the second attempt (after failing the first) is 10%. To find the conditional probability of passing on the second attempt given that the test is passed within three attempts, we calculate the total success chances and relate it to this step.

This is expressed as:
  • The chance of initially failing is 20%, then passing the second test is 50%, so the probability for the second try is 0.10 (or 10%).
  • When considering all attempts together, the total probability of passing is 93%.
  • The conditional probability for passing specifically on the second attempt, given overall success, is calculated by dividing the second attempt's passing chance by the total success probability: \(\frac{0.10}{0.93} \approx 0.1075\).
This shows how we use known probabilities to calculate the likelihood of sequential conditions in real scenarios.
Step-by-Step Solution
Breaking down problems into step-by-step solutions is an excellent way to tackle complex probability scenarios. By dissecting each stage, we can handle seemingly daunting problems with ease.

The provided solution involves several steps to answer the driving test probability questions:
  • Step 1 establishes our foundational probabilities: passing the first, second, and third attempts, which are 80%, 50%, and 30% respectively.
  • Step 2 focuses on obtaining the cumulative probability for passing by the second attempt, considering the initial failure rate.
  • Step 3 extends this idea to include the third attempt, considering failures across two attempts before success.
  • In Step 4, all calculated probabilities are summed, ensuring we account for all potential ways to pass within three tries.
  • Finally, Step 5 zeroes in on the probability of passing specifically on the second attempt, given success within three tries.
Each step builds upon prior information, helping transform a complicated problem into manageable parts. This methodical breakdown is valuable in any probability-related challenge.
Driving Test Statistics
Driving test statistics can often reveal patterns about how well individuals prepare for and cope with challenges. In our scenario, the case studies illustrate that 80% pass their driving test on the first attempt, but chances decrease significantly with subsequent attempts.

Observing these statistics is practical for understanding larger trends in skills assessment and preparation. The figures suggest that drivers who do not pass initially might benefit from additional practice or study before retaking their tests. Moreover, due to the drop in pass rates from the first to the second (50%) and even lower to the third attempts (30%), it's crucial to better understand the challenges faced by test-takers during these retries.

- Approximately 93% of drivers pass without needing a year of retraining, indicating that further efforts and multiple attempts tend to lead to eventual success. - Only about 10.75% of successful candidates passed on their second try, highlighting the importance of the first attempt in this city’s test dynamics. Such analysis provides key insights into improving the preparation strategies for students and enhancing education materials for driving instructors.

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

Driving tests in a certain city are not easy to pass the first time you take them. After going through training, the percentage of new drivers passing the test the first time is \(60 \% .\) If a driver fails the first test, there is a chance of passing it on a second try, two weeks later. \(75 \%\) of the second- chance drivers pass the test. Otherwise, the driver has to retrain and take the test after 6 months. Find the probability that a randomly chosen new driver will pass the test without having to wait 6 months.

An urn contains six red balls and two blue ones. We make two draws and each time we put the ball back after marking its colour. a) What is the probability that at least one of the balls is red? b) Given that at least one is red, what is the probability that the second one is red? c) Given that at least one is red, what is the probability that the second one is blue?

When answering a question on a multiple choice test, a student is given 5 choices, one of which is correct. The test is so designed that the choices are very close and the probability of getting the correct answer, when you know the material, is \(0.6 .\) In a class where \(70 \%\) of the students are well prepared, a randomly chosen student answers the question correctly. What is the probability that the student really knew the material?

Two dice are rolled and the numbers on the top face are observed. a) List the elements of the sample space. b) Let \(x\) represent the sum of the numbers observed. Copy and complete the following table. $$\begin{array}{|l|l|l|l|l|l|l|l|l|l|l|} \hline x & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 & 10 & 11 & 12 \\ \hline P(x) & & \frac{1}{18} & & & & & & & & & \\ \hline \end{array}$$ c) What is the probability that at least one die shows a \(6 ?\) d) What is the probability that the sum is at most \(10 ?\) e) What is the probability that a die shows 4 or the sum is \(10 ?\) f) Given that the sum is \(10,\) what is the probability that one of the dice is a \(4 ?\)

Five cards are chosen at random from a deck of 52 cards. Find the probability that the set contains a) 3 kings b) 4 hearts and 1 diamond.

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.