You were told that the amount of time lapsed between consecutive trades on the New
York Stock Exchange followed a normal distribution with a mean of 15 seconds. You
were also told that the probability that the time lapsed between two consecutive trades
to fall between 16 to 17 seconds was 13%. The probability that the time lapsed between
two consecutive trades would fall below 13 seconds was 7%. The middle 60% of the
time lapsed will fall between which two numbers?
TABLE 18-6
The maker of a packaged candy wants to evaluate the quality of her production process.
On each of 16 consecutive days, she samples 600 bags of candy and determines the
number in each day’s sample that she considers to be of poor quality. The data that she
developed follow.
Referring to Table 18-6, the estimate of the proportion of poor quality bags of candy is
________.
TABLE 13-4
The managers of a brokerage firm are interested in finding out if the number of new
clients a broker brings into the firm affects the sales generated by the broker. They
sample 12 brokers and determine the number of new clients they have enrolled in the
last year and their sales amounts in thousands of dollars. These data are presented in the
table that follows.
Referring to Table 13-4, suppose the managers of the brokerage firm want to construct a
99% confidence interval estimate for the mean sales made by brokers who have brought
into the firm 24 new clients. The confidence interval is from ________ to ________.
TABLE 6-2
John has two jobs. For daytime work at a jewelry store he is paid $15,000 per month,
plus a commission. His monthly commission is normally distributed with a mean of
$10,000 and a standard deviation of $2,000. At night he works occasionally as a waiter,
for which his monthly income is normally distributed with a mean of $1,000 and a
standard deviation of $300. John’s income levels from these two sources are
independent of each other.
Referring to Table 6-2, for a given month, what is the probability that John’s
commission from the jewelry store is at least $12,000?
TABLE 6-7
A company has 125 personal computers. The probability that any one of them will
require repair on a given day is 0.15.
Referring to Table 6-7 and assuming that the number of computers that requires repair
on a given day follows a binomial distribution, compute the probability that there will
be at least 25 computers that require repair on a given day using a normal
approximation.