1-The marks obtained by a number of student in a certain subject are approximately normally distributed with a mean 70 and standard deviation 5. if 3 students are selected at random from this group what is probability that at least 1 of them would have scored above 75 marks?
2- The time (in hours) required to repair a machine is exponentially distributed with parameter λ if the probability that the repair time exceed 2 hours period is 0.3679, evaluate λ, hence find the probability of repair time to be at most 2 hours?
3- An engineer selects 10 components at random and it is reported that the average strength of the components is between 72.3 and 75.7 with 99% confidence. what is the mean and sample standard deviation of the 10 compov