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A manufacturing firm orders computer chips from three
different companies: 10% from Company A; 20% from
Company B; and 70% from Company C. Some of the
computer chips that are ordered are defective: 4% from
Company A are defective; 2% from Company B are
defective; and 0.5% from Company C are defective. A
worker at the manufacturing firm discovers that a
randomly selected computer chip is defective. What is
the probability that the computer chip came from
Company B? Show your work.
The National Association of Retailers reports that 62% of all
purchases are now made by credit card; you think this is true at
your store as well. On a typical day you make 20 sales.
a)Explain why your sales can be considered Bernoulli trials.
b)What is the probability that your 4th customer is the first one
who uses a credit card?
c)Let X represent the number of customers who use a credit
card on a typical day. What is the probability model for X?
Specify the model (name and parameters) and tell the mean
and standard deviation.
d)What is the probability that on a typical day at least half of
your customers use a credit card?