Statistic Questin 3

QUESTION THREE

i)        If 5% of the items produced turn out to be defective. Then find out the probability that out of 25 items selected at random there are

a)       Exactly three defective                                                                                      (3 marks)

b)      At least two defective                                                                                       (3 Marks)

c)       Exactly four defective                                                                                       (3 marks)

d)      Find the mean and the variance                                                                        (3 Marks)

ii)      Bank customer arrive randomly on a week day afternoon at an average of 3.2 customers every 4 minutes

a)       What is the probability of having more than 7 customers arriving at the bank in an interval of 4 minutes?                                                                                                    (4 marks)

b)      What is the standard deviation of the number of customers arriving in a 4 minutes interval?                                                                                                                          (4 marks)