1. Continuous distributions

Hi,
Can any one help me on part(b) of the following question. I did part(a)
Q1) In the multiple-choice examination, candidate John picks his answer to each question at random from the list of 3 answers provided, of which only one is correct. A candidate answering 18 or more questions correctly passes the examination.
(a)For a paper containing 45 questions, use a normal approximation to find, to 3 decimal places, the probability that Johns passes.
(b)It is required that the probability that Johns passes should be less than 0.005. Use a normal approximation to show that the paper should contain at most 31 questions.

2. Originally Posted by Sashikala
Hi,
Can any one help me on part(b) of the following question. I did part(a)
Q1) In the multiple-choice examination, candidate John picks his answer to each question at random from the list of 3 answers provided, of which only one is correct. A candidate answering 18 or more questions correctly passes the examination.
(a)For a paper containing 45 questions, use a normal approximation to find, to 3 decimal places, the probability that Johns passes.
(b)It is required that the probability that Johns passes should be less than 0.005. Use a normal approximation to show that the paper should contain at most 31 questions.
You are given a binomial distribution and asked to use the Normal approximation to it. Find the mean and standard deviation for the given binomial distribution. They will be the mean and standard deviation for the normal approximation. Because x in the binomial distribution must be an integer, while z in the normal distribution is any real number, you want z to be any number that rounds to x: in (a) you want P(z> 18.5). In, you are asked to find N in the binomial distribution so that for the normal approximation P(z> 18.5)< 0.005.

3. Continuous distribution

Hi HallsofIvy,
Thanks. I understood.