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91Ó°ÊÓ

The probability of a student getting an A grade in an economics class is \(.24\) and that of getting a B grade is \(.28\). What is the probability that a randomly selected student from this class will get an \(\mathrm{A}\) or a \(\mathrm{B}\) in this class? Explain why this probability is not equal to \(1.0\)

Short Answer

Expert verified
The probability that a randomly selected student from this class will get an A or a B grade is 0.52.

Step by step solution

01

Identify the given probabilities

The probability of getting an A grade \(P(A)\) is given as \(0.24\) and the probability of getting a B grade \(P(B)\) is given as \(0.28\).
02

Use addition principle of probability

To find the probability of a student getting an A or B, we add the two probabilities together. That is, \(P(A \cup B) = P(A) + P(B)\).
03

Substitute and calculate

Substitute the given probabilities: \(P(A \cup B) = 0.24 + 0.28 = 0.52 \).
04

Explain the reasons the sum is not equal to 1

The total probability of an event can not be more than 1. If the probability of getting either an A or B was 1, it would mean that there are no other grades that a student can achieve, which is not the case in real-life scenario. There are other grades (C, D, E, F) that a student can get in an economics class, which is why the probability of getting an A or B does not equate to 1.

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Key Concepts

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

Addition Principle
In probability theory, the addition principle, also known as the sum rule, helps us understand the ways in which we can calculate the probability of one of several possible events happening. This principle is particularly useful when we want the probability that one or another event will occur. For example, if we have two events, A and B, the principle states that the probability of A or B happening is the sum of the probability of each event happening individually, assuming that there is no overlap between events.

In a classroom setting, if the probability of a student receiving an "A" in economics is 0.24 and a "B" is 0.28, the addition principle tells us to add these probabilities to find the chance of a student receiving either an "A" or "B" grade. This simple addition, when the events are mutually exclusive, ensures we consider all potential positive outcomes.
Probability of Events
The probability of an event is a measure of the likelihood that the event will occur as a result of a random experiment. It is expressed as a number between 0 and 1, where 0 indicates impossibility and 1 indicates certainty.

For instance, in the context of receiving grades, if an event represents receiving a particular grade like "A" or "B," the probability associated with that event helps students understand how likely it is to achieve these grades. In the original exercise, the probabilities of receiving "A" and "B" grades were given as 0.24 and 0.28 respectively. These values reflect the likelihood based on past performance data or statistical predictions.

It’s essential to remember:
  • Probabilities must always sum up to 1 when considering all possible outcomes or grades.
  • An event's probability cannot exceed 1, in any given situation.
Real-Life Scenarios
In real-life situations, understanding the probability of events helps in decision-making and predicting outcomes.

For example, knowing the likelihood of certain grades can help students strategize their study plans. If students are aware of low probabilities of achieving certain high grades, they might focus more on topics of struggle or seek additional help. Conversely, higher probabilities could reinforce their current study strategies.

Moreover, teachers and educators can use these probabilities to identify areas where students might be struggling as a group and to focus educational efforts there. Probabilities act as a guide, providing insights that are not only academic but also practical, tailoring educational experiences to meet the students' needs.
Grades in Education
Grades serve as a standard measure of achievement in academics. They reflect a student's understanding, commitment, and ability to apply knowledge. Probabilities associated with grades help educators, students, and even parents gauge expectations and performance standards.

In this context, the probabilities of receiving different grades demonstrate the variation in student performance. It reflects not only the difficulty of a course but also the efficacy of teaching strategies and student engagement levels.

Educational systems use grades to assess:
  • Curriculum strengths and weaknesses.
  • Student comprehension and application skills.
  • Effectiveness of teaching methods.
These measures are integral in continuously enhancing learning frameworks and ensuring students are well-prepared to meet educational goals as well as be competent in their future endeavors.

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Most popular questions from this chapter

Two thousand randomly selected adults were asked if they think they are financially better off than their parents. The following table gives the two- way classification of the responses based on the education levels of the persons included in the survey and whether they are financially better off, the same as. or worse off than their parents. $$\begin{array}{lccc} \hline & \begin{array}{c} \text { Less Than } \\ \text { High School } \end{array} & \begin{array}{c} \text { High } \\ \text { School } \end{array} & \begin{array}{c} \text { More Than } \\ \text { High School } \end{array} \\ \hline \text { Better off } & 140 & 450 & 420 \\ \text { Same as } & 60 & 250 & 110 \\ \text { Worse off } & 200 & 300 & 70 \end{array}$$ Suppose one adult is selected at random from these 2000 adults. Find the following probabilities. a. \(P(\) better off or high school \()\) b. \(P(\) more than high school or worse off \()\) c. \(P\) (better off or worse off)

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Let \(A\) be the event that a number less than 3 is obtained if we roll a die once. What is the probability of \(A ?\) What is the complementary event of \(A\), and what is its probability?

Given that \(A\) and \(B\) are two independent events, find their joint probability for the following. a. \(P(A)=.61\) and \(P(B)=.27\) b. \(P(A)=.39\) and \(P(B)=.63\)

A gambler has given you two jars and 20 marbles. Of these 20 marbles, 10 are red and 10 are green You must put all 20 marbles in these two jars in such a way that each jar must have at least one marble in it. Then a friend of yours, who is blindfolded, will select one of the two jars at random and then will randomly select a marble from this jar. If the selected marble is red, you and your friend win \(\$ 100\) a. If you put 5 red marbles and 5 green marbles in each jar, what is the probability that your friend selects a red marble? b. If you put 2 red marbles and 2 green marbles in one jar and the remaining marbles in the other jar, what is the probability that your friend selects a red marble? c. How should these 20 marbles be distributed among the two jars in order to give your friend the highest possible probability of selecting a red marble?

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