Given the pdf for a particular exam , identify the cut-off for students scoring in the top 30%. [Hint: If the solution is difficult to obtain analytically, set up the expression to be solved and substitute the various choices below.]
A) 70
B) 73
C) 76
D) 17.6

Question

Given the pdf for a particular exam  , identify the cut-off for students scoring in the top 30%. [Hint: If the solution is difficult to obtain analytically, set up the expression to be solved and substitute the various choices below.]
A) 70 
B) 73 
C) 76 
D) 17.6

Quizplus · Accepted Answer

Since we are trying to find the cut-off for the top 30%, we need to find the value of x such that Pr(X > x) = 0.3. We can solve this numerically using a calculator or software, or we can use the answer choices as suggested in the hint. 
Substituting each answer choice into the equation Pr(X > x) = 0.3, we find that only choice B, x = 73, gives us a probability close to 0.3 (specifically, Pr(X > 73) = 0.298). Therefore, B is the best choice.

Given the Pdf for a Particular Exam , Identify