There are 40 students in an elementary statistics class. On the basis of years o
ID: 3352854 • Letter: T
Question
There are 40 students in an elementary statistics class. On the basis of years of experience, the Instructor knows that the time needed to grade a randomly chosen first examination paper is a random variable with an expected value of 6 min and a standard deviation of 5 min. (Round your answers to four decimal places.) (a) If grading times are independent and the instructor begins grading at 6:50 P.M. and before the 11:00 P.M. TV news begins? a grades continuously, what is the (approximate) probability that he is through greding (b) If the sports report begins at 11:10, what is the probability that he misses part of the report if he waits until grading is done before turning on the TV? You may need to use the appropriate table in the Appendix of Tables to a Need Help? answer this questionExplanation / Answer
z = (x – ) / (/sqrt(n))
a) =6, =5
6.50PM to 11PM = 250mins for 40 students
Thus minutes per student = 250/40 = 6.25mins
Thus, x =6.25.
If show is not missed work is done before 11PM. Thus, time taken < 250 mins
Thus, x <= 6.25
Z = (6.25-6)/(5/sqrt(40)) = 0.32
P(x<=6.25) = P(z<=0.32) = 0.6255
b) =6, =5
6.50PM to 11.10PM = 260mins for 40 students
Thus minutes per student = 260/40 = 6.5mins
Thus, x =6.5
If show is missed work is not done before 11.10PM. Thus, time taken > 260 mins
Thus, x >= 6.5
Z = (6.5-6)/(5/sqrt(40)) = 0.63
P(x>=6.5) = P(z>=0.63) = 0.2643
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