Here is a simple probability model for multiple-choice tests. Suppose that each

Question

Here is a simple probability model for multiple-choice tests. Suppose that each student has probability p of correctly answering a question chosen at random from a universe of possible questions. (A strong student has a higher p than a weak student.) The correctness of answers to different questions are independent. Jodi is a good student for whom p = 0.76. (a) Use the Normal approximation to find the probability that Jodi scores 71% or lower on a 100-question test. (Round your answer to four decimal places.) .1208 Correct: Your answer is correct. (b) If the test contains 250 questions, what is the probability that Jodi will score 71% or lower? (Use the normal approximation. Round your answer to four decimal places.) .0320 Correct: Your answer is correct. (c) How many questions must the test contain in order to reduce the standard deviation of Jodi's proportion of correct answers to half its value for a 100-item test? This is the fourth time I am asking this question just for C. Answers for A and B are in bold. I have answered 100 and 25 for C and they are both incorrect. Please help me with C.

Explanation / Answer

here as we know that std deviation =(p(!-p)/n)1/2

as std deviation is inverely proportional to square root of n

therefore to half its value for a 100-item test ; test must contain 100*22 =400 question

please revert for any clarification.

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