2. There are 40 students in an elementary statistics course. On the basis of years of experience, the instructor knows that the time needed to grade a randomly chosen examination is a random variable with an expected time of 6 minutes and standard deviation of 6 minutes.
(a) If grading times are independent and the instructor begins grading at 6:50 pm and grades continuously, what is the probability that the instructor is through grading before 11:00 pm?
(b) If the sports report begins at 11:10 pm, what is the probability that the instructor misses part of the report if the instructor waits until grading is done before turning on the TV?
5. The time it takes for a taxi to drive from the office to the airport was recorded
on 50 occasions. It was found that ¯x = 31 minutes and s = 3. Find:
(a) an estimate for μ, the population mean time to drive to the airport,
(b) the estimated standard error of the estimate obtained in part (a),
(c) an approximate 95.4% error margin, and
(d) the factor that the sample size should be increased to reduce the estimated standard error in part (b) to 1/3 of its original value.
(a) If grading times are independent and the instructor begins grading at 6:50 pm and grades continuously, what is the probability that the instructor is through grading before 11:00 pm?
(b) If the sports report begins at 11:10 pm, what is the probability that the instructor misses part of the report if the instructor waits until grading is done before turning on the TV?
5. The time it takes for a taxi to drive from the office to the airport was recorded
on 50 occasions. It was found that ¯x = 31 minutes and s = 3. Find:
(a) an estimate for μ, the population mean time to drive to the airport,
(b) the estimated standard error of the estimate obtained in part (a),
(c) an approximate 95.4% error margin, and
(d) the factor that the sample size should be increased to reduce the estimated standard error in part (b) to 1/3 of its original value.