--------------------------------~-~ Stat 100 Exam 2A Spring 2005 Calculators allowed All work must be shown to receive full credit. 1. 60% of flights at an airport depart on time. Determine the probability that, of 14 randomly selected flights: a) (5 pts) at least 6 depart on time b) (5 pts) at most 5 do not depart on time c) (5 pts) exactly 8 depart on time. d) (5 pts) Use the normal approximation to find the approximate probability that out of350 randomly selected flights, less than 200 depart on time. 2. For the probability density function depicted at right: .2 bf(X) 5 a) (6 pts) find P(2 < X < 3) b) (6 pts) find P(X> 3) c) (8 pts) find the median and the quartiles. 3. For the standard normal variable, Z, find: a) (6 pts) P(Z> -1.79) b) (7 pts) z such that P(-.6 < Z < z) =.5 c) (7 pts) the 40 th percentile of the standard normal distribution. 4. A survey finds that students at a university use computers an average of7 hours per week with standard deviation ...