1     Poisson Distribution
Exercise Set 1
    1. Calls come in to a telephone exchange at random but at a rate of 300 per hour(when
       taken over a long period). Assume that the number of calls coming in during a given
       period is a random variable with a poisson distribution and determine the probability
       that
       (1) one call comes in during a given one-minute period.
       (2) at least two calls come in during a given one-minute period.
       (3) no calls arrive in an interval of length T minutes.
    2. ’Joints’ in a certain manufactured tape occur at random, but on an average of one per
       2000 feet. Assuming a Poisson distribution, what is the probability that a 5000-foot
       roll of tape has
       (1) no joints.
       (2) at most two joints.
       (3) at least two joints.
    3. Flaws in gold plating of large sheets of metal occur at random, on the average of one
       in each section of area 10 square feet. What is the probability that a sheet 5 by 8 will
       have no flaws? At most one flaw?.
    4. The numbers of arrivals of customers during any day follows Poisson distribution with
       a mean of 5. What is the probability that the total number of customers on two days
       selected at random is less than 2?
    5. Suppose 3% of bolts made by a machine are defective, the defects occurring at random
       during production. If bolts are packaged 50 per box, find exact probability and Poisson
       approximation to it, that a given box will contain 5 defectives.
    6. Using Poisson distribution, find the probability that the ace of spades will be drawn
       from a pack of well-shuffled cards at least once in 104 consecutive trials.
    7. If the probability that an individual suffers a bad reaction from a certain injection is
       0.001, determine the probability that out of 2000 individuals
       (1) exactly3,
       (2) more than 2 individuals,
       (3) none, (4) more than one individual will suffer a bad reaction.
    8. In a certain factory turning out a razor blades, there is a small chance of 0.002 for
       any blade to be defective. The blades are supplied in packets of 10, use appropriate
       and suitable distribution to calculate the approximate number of packets containing
       no defective, one defective and two defective blades respectively in a consignment of
       50,000 packets.
    9. A car hire firm has two cars which it hires out day by day. The number of demands
       for a car on each day is distributed as a Poisson distribution with mean 1.5. Calculate
       the number of days in a year on which
       (1) car is not used. (2) the number of days in a year some demand is refused.
10. Suppose that a book of 600 pages contains 40 printing mistakes. Assume that these
    errors are randomly distributed throughout the book and x, the number of error per
    page has a Poisson distribution. What is the probability that 10 pages selected at
    random will be free of errors?