Question 1
Use the standard normal distribution table to find
2 marks a. .
2 marks b. .
Question 2
Test scores on a university admissions test are normally distributed, with a mean of 500 and a standard deviation of 100.
4 marks a. What is the probability that a randomly selected applicant scores between 425 and 575?
4 marks b. What is the probability that a randomly selected applicant scores 625 or more?
2 marks c. What is the probability that a randomly selected applicant scores less than 500?
4 marks d. Twenty per cent of test scores exceed what value?
Question 3
4 marks The life span of a DVD player produced by one major company is known to be normally distributed with a mean of 6.2 years. If 4.01% of these DVD players have a life span of more than 8 years, what is the standard deviation of the DVD player’s life span?
Question 4
It is estimated that, in jury trials, the jury will reach the correct decision (guilty or not guilty) 92% of the time. In 200 randomly selected jury trials,
4 marks a. what is the probability that the jury will reach the correct decision in at least 175 of the trials?
3 marks b. what is the probability that there will be fewer than 180 correct decisions?
4 marks c. What is the probability that there will be exactly 184 correct decisions?