Write short notes about
i. Biased error
ii. Unbiased error
iii. Normal distribution
2. The demand for a particular type of pump at an isolated mine is random and independent of
previous occurrences, but the average demand in a week (7 days) is for 2.8 pumps. Further
supplies are ordered each Tuesday morning and arrive on the weekly plane on Friday morning.
Last Tuesday morning only one pump was in stock, so the storesman ordered six more to come
in Friday morning. Assume that the requirements of the Poisson distribution are satisfied. Find
the probability that one pump will still be in stock on Friday morning when new stock arrives.
3. Suppose that during any hour in a large department store, the average number of shoppers is
448, with a standard deviation of 21 shoppers. What is the probability that a random sample of
49 different shopping hours will yield a sample mean between 441 and 446 shoppers?