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A professor surveyed students in her morning and afternoon Math 105 class, and asked what their class standing was. The class standings are summarized below: $$ \begin{array}{|c|c|c|c|c|c|} \hline & \text { Freshman } & \text { Sophomore } & \text { Junior } & \text { Senor } & \text { Total } \\ \hline \text { Morning Class } & 12 & 5 & 7 & 8 & 32 \\ \hline \text { Afternoon Class } & 5 & 13 & 8 & 2 & 28 \\ \hline \text { Total } & 17 & 18 & 15 & 10 & 60 \\ \hline \end{array} $$ If one student was chosen at random: a. What is the probability they were in the morning class? b. What is the probability they were a Freshman? c. What is the probability that they were a Senior and they were in the afternoon class? d. What is the probability that they were a Sophomore given they were in the morning class? e. What is the probability that they were in the morning class or they were a Junior?

Short Answer

Expert verified
a. \(\frac{8}{15}\); b. \(\frac{17}{60}\); c. \(\frac{1}{30}\); d. \(\frac{5}{32}\); e. \(\frac{2}{3}\).

Step by step solution

01

Identifying Total Number of Students

The total number of students surveyed is the sum of students in both classes, which is 60 students.
02

Probability of Being in Morning Class

To find the probability of a student being in the morning class, divide the number of morning class students (32) by the total number of students (60). Thus, the probability is \( \frac{32}{60} = \frac{8}{15} \).
03

Probability of Being a Freshman

The probability of being a Freshman is the total number of Freshmen (17) divided by the total number of students (60). Therefore, the probability is \( \frac{17}{60} \).
04

Probability of Being a Senior in Afternoon Class

This probability is calculated by dividing the number of Seniors in the afternoon class (2) by the total number of students (60). Hence, the probability is \( \frac{2}{60} = \frac{1}{30} \).
05

Probability of Being a Sophomore Given They Are in Morning Class

Here, we need to find the probability of being a Sophomore among morning class students. The formula is to divide the number of Sophomores in the morning class (5) by the total number of students in the morning class (32). Thus, the probability is \( \frac{5}{32} \).
06

Probability of Being in Morning Class or Being a Junior

Calculate the probability of the union of two events: being in the morning class or being a Junior. Use the formula for the probability of the union of two events: \( P(A \cup B) = P(A) + P(B) - P(A \cap B) \). Here, \( P(A) = \frac{32}{60} \) (morning class), \( P(B) = \frac{15}{60} \) (Juniors), and \( P(A \cap B) = \frac{7}{60} \) (Juniors in morning class). Thus, \( P(A \cup B) = \frac{32}{60} + \frac{15}{60} - \frac{7}{60} = \frac{40}{60} = \frac{2}{3} \).

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Key Concepts

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

Conditional Probability
Conditional probability is a fundamental concept in probability theory that measures the likelihood of an event occurring given that another event has already occurred. It's crucial in situations where the occurrence of one event affects the probability of another event. In our exercise, we can see conditional probability in action when we calculate the probability of a student being a Sophomore, given they are in the morning class.

To find conditional probability, we use the formula:
  • \( P(A|B) = \frac{P(A \cap B)}{P(B)} \)
Where \( P(A|B) \) is the probability of event \( A \) given that \( B \) has occurred, \( P(A \cap B) \) is the probability of both events happening, and \( P(B) \) is the probability of event \( B \).

In Step 5 of the solution, we need \( P(A|B) \), where event \( A \) is 'being a Sophomore' and event \( B \) is 'being in the morning class.' We find this by taking the number of Sophomores in the morning class and dividing it by the total number of students in the morning class. So, \( P(A|B) = \frac{5}{32} \). Understanding this concept helps in calculating probabilities where conditions or constraints are applied, enhancing our decision-making processes in various fields.
Class Survey Analysis
Class survey analysis can often involve understanding different statistical measures from data collected in surveys. Surveys like the one conducted by the professor can be analyzed using simple probability to determine interesting insights about the class composition.

Let's break down the survey data from the exercise. The survey asks for class standings among students, tallying their distribution across two classes: morning and afternoon. This setup is perfect for calculating various probabilities. For instance:
  • The probability that a random student was in the morning class, \( \frac{8}{15} \), is simply the ratio of morning class students to the total surveyed students.
  • The probability of randomly selecting a Freshman is found by dividing the number of Freshmen by the total number of students, \( \frac{17}{60} \).
By understanding the survey data and applying these probabilities, one gains insights into the composition and distribution of students and can ask more targeted questions about different groups. Such analyses are valuable tools for educators and administrators in tailoring educational programs to the needs of diverse student bodies.
Mathematical Problem Solving
Mathematical problem-solving involves applying mathematical concepts and methods to solve various problems. In the class survey problem, logical reasoning and mathematical formulas are essential tools. These tools help us break down complex situations into manageable parts.

To effectively solve problems like those in the exercise, it's important to follow a step-by-step approach:
  • First, clearly understand the problem by identifying all given data and what is being asked.
  • Next, apply relevant mathematical principles or formulas, such as the probability of events and their combinations.
This method is evident in the exercise, particularly in Step 6, where we are tasked with finding the probability that a student is either in the morning class or a Junior. By using the formula for the union of two events, we can compute this probability:
  • \( P(A \cup B) = P(A) + P(B) - P(A \cap B) \)
Which results in \( \frac{2}{3} \).
By cultivating these problem-solving skills, students enhance their ability to tackle a wide range of mathematical challenges, fostering a deeper understanding and appreciation of mathematics.

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