Question

When taking a test with m closed answers, a student knows the correct answer with probability p, otherwise he chooses one of the possible answers at random. What is the probability that the student knows the correct answer given that he answered the question correctly.

182

likes
912 views

Answer to a math question When taking a test with m closed answers, a student knows the correct answer with probability p, otherwise he chooses one of the possible answers at random. What is the probability that the student knows the correct answer given that he answered the question correctly.

Expert avatar
Frederik
4.6
100 Answers
To solve this problem, we can use Bayes' theorem.

Let's denote the following events:
A: The event that the student knows the correct answer.
B: The event that the student answered the question correctly.

We are asked to find P(A|B), the probability that the student knows the correct answer given that he answered the question correctly.

According to Bayes' theorem, we have:

P(A|B) = \frac{{P(B|A) \cdot P(A)}}{{P(B)}}

We can calculate each of these probabilities step-by-step:

1. P(A) is the probability that the student knows the correct answer. This is given as p.
2. P(B|A) is the probability that the student answered the question correctly given that he knows the correct answer. This is equal to 1 since we are assuming that the student knows the correct answer.
3. P(B) is the total probability that the student answered the question correctly.

To calculate P(B), we need to consider two cases:
a) The student knows the correct answer, which happens with probability p.
b) The student does not know the correct answer, which happens with probability 1 - p. In this case, the probability of answering correctly by randomly choosing one of the possible answers is 1/m.

Therefore, we have:

P(B) = P(A) \cdot 1 + (1 - P(A)) \cdot \frac{1}{m} = p + \frac{1 - p}{m}

Now we can substitute these values back into Bayes' theorem to find P(A|B):

P(A|B) = \frac{{1 \cdot p}}{{p + \frac{1 - p}{m}}} = \frac{{p \cdot m}}{{pm + 1 - p}}

Answer: The probability that the student knows the correct answer given that he answered the question correctly is \frac{{p \cdot m}}{{pm + 1 - p}}

Frequently asked questions (FAQs)
Question: In a right triangle, if one angle measures 30 degrees and the hypotenuse is 10 units long, what is the length of the opposite side?
+
Math question: For the linear function f(x) = x, if x is increased by 3, what is the corresponding increase in the output value?
+
Math question: Solve for x: log₂(x) + log₃(x) = 5.
+
New questions in Mathematics
Calculate to represent the function whose graph is a line that passes through the points (1,2) and (−3,4). What is your slope?
A pump with average discharge of 30L/second irrigate 100m wide and 100m length field area crop for 12 hours. What is an average depth of irrigation in mm unIt?
a ferry travels 1/6 of the distance between two ports in 3/7 hour. the ferry travels at a constant rate. at this rate, what fraction of the distance between the two ports can the ferry travel in one hour?
5 squirrels were found to have an average weight of 9.3 ounces with a sample standard deviation is 1.1. Find the 95% confidence interval of the true mean weight
The gross domestic product the gdp for the United States in 2017 was approximately $2.05x10^3. If you wrote this number in standard notation , it would be 205 followed by how many zeros
Revenue Maximization: A company sells products at a price of $50 per unit. The demand function is p = 100 - q, where p is the price and q is the quantity sold. How many units should they sell to maximize revenue?
Consider the relation R defined on the set of positive integers as (x,y) ∈ R if x divides y. Choose all the true statements. R is reflexive. R is symmetric. R is antisymmetric. R is transitive. R is a partial order. R is a total order. R is an equivalence relation.
*Question!!* *Victory saved 3,000 in first bank and 2,000 Naira in union bank PSC with interest rate of X% and Y% per annual respectively his total interest in one year is #640. If she has saved 2,000 naira with first bank and 3,000 naira in union bank for same period she would have made extra 20# as additional interest, then find the value of X and Y
In a normally distributed data set a mean of 31 where 95% of the data fall between 27.4 and 34.6, what would be the standard deviation of that data set?
A job takes 9 workers 92 hours to finish. How many hours would it take 5 workers to complete the same job?
Divide 22 by 5 solve it by array and an area model
how many arrangement can be made of 4 letters chosen from the 8 letters of the world ABBSOLUTE
TEST 123123+1236ttttt
Buffalo Company makes and sells shampoo. Each unit requires $1.40 labor costs, material costs per unit are $0.90 and other variable costs are $0.30. It sells shampoo for $4.45 to retailers. Fixed costs are $15,000. It sold 25,000 units in the current month. What is the Break-Even point in units? What is the Break-Even point in dollars? What is the contribution margin of Buffalo Company?
2x2
factor the polynomial completely over the set of complex numbers b(x)=x^4-2x^3-17x^2+4x+30
To get to a hotel on the hill you have to travel 6 km of uphill road and every kilometer there are 6 sharp curves. Each of the sharp curves is marked by three traffic signs. How many traffic signs are there on the stretch of road that leads to the arbergi?
7- A printing company found in its investigations that there were an average of 6 errors in 150-page prints. Based on this information, what is the probability of there being 48 errors in a 1200-page job?
solve R the following equation 4 x squared - 35 - 9 over x squared is equal to 0
Triangle ABC has AB=AC and angle BAC =X, with X being less than 60 degrees. Point D lies on AB such that CB = CD Point E lies on AC such that CE= DE Determine angle DEC in terms of X