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91Ó°ÊÓ

Stanley's statistics seminar is graded on a Pass/Fail basis. At the end of the semester each student is given the option of taking either a two-question exam (Final A) or a three-question exam (Final B). To pass the course, students must answer at least one question correctly on whichever exam they choose. The professor estimates that a typical student has a \(45 \%\) chance of correctly answering each of the two questions on Final A and a \(30 \%\) chance of correctly answering each of the three questions on Final B. Which exam should Stanley choose? Answer the question two different ways.

Short Answer

Expert verified
Stanley should choose Final A because it has a higher passing probability.

Step by step solution

01

Calculating the Probability for Final A

The probability of Stanley correctly answering each question in Final A is \(45 \%\). Since there are two questions, the probability of passing (answering at least one question correctly) is \(1 - \) the probability of failing all questions = \(1 - (1 - 0.45)^2 = 0.6975.\)
02

Calculating the Probability for Final B

The probability of Stanley correctly answering each question in Final B is \(30 \% \). Since there are three questions, the probability of passing (answering at least one question correctly) is \(1 - \) the probability of failing all questions = \(1 - (1 - 0.30)^3 = 0.657.\)
03

Choosing the Best Option

Stanley should choose the exam with the higher passing probability. Comparing the two probabilities, \(0.6975 > 0.657\), therefore, Final A has a higher chance of passing.

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Key Concepts

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

Probability Calculation
When it comes to making decisions under uncertainty, understanding probability calculations is crucial. To determine the best choice for Stanley's exam, we need to compute the likelihood of passing each exam.

First, let's delve into **Final A**, which consists of two questions. The probability of getting any single question right is 45%. To calculate the chance of failing all questions, it's necessary to find the probability of getting both wrong. The probability of getting a question wrong is 1 minus the probability of getting it right, which is \( 1 - 0.45 = 0.55 \). Now, for the two questions:
  • The probability of failing both is \( 0.55 \times 0.55 = 0.3025 \).
Therefore, the probability of passing (getting at least one question right) is \( 1 - 0.3025 = 0.6975 \).

Next, for **Final B**, there are three questions, each with a 30% probability of being answered correctly. Similarly, we calculate the chance of failing all:
  • The probability of failing a question is \( 1 - 0.30 = 0.70 \).
  • The probability of failing all three questions is \( 0.70 \times 0.70 \times 0.70 = 0.343 \).
Hence, the probability of passing is \( 1 - 0.343 = 0.657 \).

Through these calculations, we gain insight into which option offers the best chance of success.
Pass/Fail Grading System
In many courses, the pass/fail grading system simplifies student outcomes into two categories: pass or fail. This binary system uses a threshold to determine if a student has met the minimum required competency.

For Stanley, this means he needs to answer at least one question correctly to pass, regardless of whether he chooses Final A or Final B. With this system:
  • Performance on individual components (questions) contributes to an overall outcome.
  • No partial credit is awarded; it's an all-or-nothing situation for each exam.
The pass/fail grading system emphasizes clearing a basic level of understanding rather than distinguishing levels of mastery. This can also relieve pressure compared to numerical grades, as students focus on reaching minimum adequacy.

When choosing between test options like Stanley's, evaluating probabilities becomes decisive, allowing students to strategize effectively to meet the required standard.
Statistical Reasoning
Statistical reasoning plays a vital role in decision-making processes, especially under conditions of uncertainty. By applying statistical methods, one can evaluate the likelihood of different outcomes and make informed choices.

For Stanley, statistical reasoning involves:
  • Understanding probabilities: Knowing the chance of getting questions right or wrong.
  • Evaluating outcomes: Determining which exam provides a higher probability of passing.
Choosing which exam to take wasn't random; it was a decision grounded in comprehending statistical probabilities.

With both, Final A and Final B options presented, Stanley applied statistical logic to assess and compare probabilities, leading him to make a decision that maximizes his passing chances. This process illustrates the power of statistical reasoning in everyday decision-making, highlighting its importance beyond purely academic calculations.

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