# Thread: Probability Problem To Resolve

1. ## Probability Problem To Resolve

Hi,

I need the solution to this problem to be able to resolve a situation at work. I believe some probability equation must be involved.

Problem:

There are 60 math teachers at a math competition conference meeting. All 60 teachers are asked to take the same math test to compare average score results. Unfortunately, there is no one else available to be grading all the tests so the teachers have to grade the tests themselves.

To eliminate any kind of margin of error, each teacher is asked to grade 20 tests of their peers, selected at random. Each graded test corresponds to one score. At the end, the teacher's final score for the test will be equal to the average of all the scores that have been graded from the other teachers.

How many scores will each teacher receive if all 60 teachers grade 20 tests of their peers selected at random?

2. ## Re: Probability Problem To Resolve

If I'm understanding you correctly then on average the answer is 20

3. ## Re: Probability Problem To Resolve

Hi Dason,

Thank you for your reply. Since there are 60 teachers and they are all grading 20 tests selected at random, how can we make sure that each of the teachers receive the same amount of graded tests in the end? Shouldn't there be a probability variable that takes into account the fact that each teacher's test has 1 chance out of 3 to be graded by any given teacher? (ratio between 60/20= 3)

The total amount of final scores in the end is still 60 (1 per teacher) but we will be averaging 60 x 20 graded scores = 1200 scores.

I just want to figure out the percentage of graded tests per teacher that will be reviewed by others and compare that data with the total number of graded scores if that makes any sense.

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